{"segment":[{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["20-x"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/10.jpg' \/><\/center>T\u1ed5ng hai s\u1ed1 l\u00e0 $20$. N\u1ebfu g\u1ecdi s\u1ed1 th\u1ee9 nh\u1ea5t l\u00e0 $x$ th\u00ec s\u1ed1 th\u1ee9 hai l\u00e0:_input_","hint":"","explain":"<span class='basic_left'>V\u00ec t\u1ed5ng hai s\u1ed1 l\u00e0 $20$ n\u00ean s\u1ed1 th\u1ee9 hai l\u00e0 $20-x$<br\/><span class='basic_pink'>V\u1eady bi\u1ec3u th\u1ee9c c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $20-x$<\/span><\/span>"}]}],"id_ques":941},{"time":24,"part":[{"title":"Ch\u1ecdn <u>nh\u1eefng<\/u> \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"checkbox","correct":[["2","3"]],"list":[{"point":10,"img":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/13.jpg' \/><\/center>Hai xe \u00f4 t\u00f4 c\u00f9ng \u0111i t\u1eeb $A$ \u0111\u1ebfn $B$. Bi\u1ebft xe th\u1ee9 nh\u1ea5t \u0111i nhanh h\u01a1n xe th\u1ee9 hai l\u00e0 $5 \\,km\/h$. V\u1eadn t\u1ed1c xe th\u1ee9 nh\u1ea5t v\u00e0 xe th\u1ee9 hai l\u1ea7n l\u01b0\u1ee3t l\u00e0:","hint":"","column":2,"number_true":2,"select":["A. $x$ v\u00e0 $x+5$","B. $x$ v\u00e0 $x-5$","C. $x+5$ v\u00e0 $x$","D. $x-5$ v\u00e0 $x$"],"explain":"<span class='basic_left'>N\u1ebfu g\u1ecdi v\u1eadn t\u1ed1c c\u1ee7a xe th\u1ee9 nh\u1ea5t l\u00e0 $x$ ($km\/h,\\,x>0$) th\u00ec v\u1eadn t\u1ed1c c\u1ee7a xe th\u1ee9 hai l\u00e0 $x-5$ ($km\/h$)<br\/>N\u1ebfu g\u1ecdi v\u1eadn t\u1ed1c c\u1ee7a xe th\u1ee9 hai l\u00e0 $x$ ($km\/h,\\,x>0$) th\u00ec v\u1eadn t\u1ed1c c\u1ee7a xe th\u1ee9 nh\u1ea5t l\u00e0 $x+5$ ($km\/h$)<br\/><span class='basic_pink'>Do v\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 c\u1ea3 B v\u00e0 C<\/span><\/span>"}]}],"id_ques":942},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0110\u00fang ho\u1eb7c Sai","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/12.jpg' \/><\/center>Cho hai s\u1ed1, bi\u1ebft $2$ l\u1ea7n s\u1ed1 l\u1edbn b\u1eb1ng $3$ l\u1ea7n s\u1ed1 b\u00e9. N\u1ebfu g\u1ecdi s\u1ed1 b\u00e9 h\u01a1n l\u00e0 $x$ th\u00ec s\u1ed1 l\u1edbn l\u00e0 $\\dfrac {2}{3}x$","select":["\u0110\u00fang","Sai"],"hint":"","explain":" <span class='basic_left'>V\u00ec $2$ l\u1ea7n s\u1ed1 l\u1edbn b\u1eb1ng $3$ l\u1ea7n s\u1ed1 b\u00e9 n\u00ean s\u1ed1 l\u1edbn b\u1eb1ng $\\dfrac 3 2$ s\u1ed1 b\u00e9. V\u1eady n\u1ebfu s\u1ed1 b\u00e9 l\u00e0 $x$ th\u00ec s\u1ed1 l\u1edbn l\u00e0 $\\dfrac 3 2 x$.<br\/><span class='basic_pink'>Do v\u1eady kh\u1eb3ng \u0111\u1ecbnh tr\u00ean l\u00e0 Sai.<\/span><br\/><span class='basic_green'>Ghi nh\u1edb:<\/span> N\u1ebfu $ax=by$ th\u00ec $\\dfrac {x}{y}=\\dfrac{b}{a}$<\/span>","column":2}]}],"id_ques":943},{"time":24,"part":[{"title":"Ch\u1ecdn <u>4<\/u> \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"checkbox","correct":[["1","2","4","5"]],"list":[{"point":5,"img":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/13.jpg' \/><\/center>Ph\u01b0\u01a1ng tr\u00ecnh bi\u1ec3u th\u1ecb b\u00e0i to\u00e1n: T\u00ecm hai s\u1ed1 t\u1ef1 nhi\u00ean. Bi\u1ebft hai s\u1ed1 t\u1ef1 nhi\u00ean c\u00f3 t\u1ed5ng l\u00e0 $80$ v\u00e0 t\u1ec9 s\u1ed1 l\u00e0 $\\dfrac {3} {5}$","hint":"","column":1,"number_true":3,"select":["A. G\u1ecdi m\u1ed9t s\u1ed1 l\u00e0 $x$. Ph\u01b0\u01a1ng tr\u00ecnh: $\\dfrac{x}{80-x}=\\dfrac{3}{5}$","B. G\u1ecdi s\u1ed1 l\u1edbn l\u00e0 $x$. Ph\u01b0\u01a1ng tr\u00ecnh: $x+\\dfrac {3} {5} x =80$ ","C. G\u1ecdi s\u1ed1 b\u00e9 l\u00e0 $x$ th\u00ec s\u1ed1 l\u1edbn l\u00e0 $\\dfrac{3}{5}x$. Ph\u01b0\u01a1ng tr\u00ecnh: $x+\\dfrac{3}{5}x=80$","D. G\u1ecdi s\u1ed1 b\u00e9 l\u00e0 $x$ th\u00ec s\u1ed1 l\u1edbn l\u00e0 $\\dfrac{5}{3}x$. Ph\u01b0\u01a1ng tr\u00ecnh: $x+\\dfrac{5}{3}x=80$","E. G\u1ecdi m\u1ed9t s\u1ed1 l\u00e0 $x$. Ph\u01b0\u01a1ng tr\u00ecnh: $\\dfrac{80-x}{x}=\\dfrac{3}{5}$"],"explain":"<span class='basic_left'>B\u00e0i gi\u1ea3i c\u00f3 nh\u1eefng tr\u01b0\u1eddng h\u1ee3p g\u1ecdi \u1ea9n sau:<br\/><b> Tr\u01b0\u1eddng h\u1ee3p 1:<\/b> G\u1ecdi m\u1ed9t trong hai s\u1ed1 l\u00e0 $x$ ($x\\in \\mathbb N^*$)<br\/>V\u00ec t\u1ed5ng hai s\u1ed1 l\u00e0 $80$ n\u00ean s\u1ed1 c\u00f2n l\u1ea1i l\u00e0 $80-x$<br\/> Hai s\u1ed1 c\u00f3 t\u1ec9 l\u1ec7 l\u00e0 $\\dfrac {3}{5}$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\dfrac{x}{80-x}=\\dfrac{3}{5}$<br\/>Ho\u1eb7c $\\dfrac{80-x}{x}=\\dfrac{3}{5}$<br\/>V\u1eady \u0111\u00e1p \u00e1n A v\u00e0 E \u0111\u00fang<br\/><b>Tr\u01b0\u1eddng h\u1ee3p 2: <\/b> G\u1ecdi s\u1ed1 l\u1edbn l\u00e0 $x\\,(x\\in\\mathbb N^*)$<br\/>V\u00ec hai s\u1ed1 c\u00f3 t\u1ec9 s\u1ed1 l\u00e0 $\\dfrac {3}{5}$ n\u00ean s\u1ed1 b\u00e9 b\u1eb1ng $\\dfrac {3}{5}$ s\u1ed1 l\u1edbn hay s\u1ed1 b\u00e9 l\u00e0 $\\dfrac {3}{5}x$. <br\/>Ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $x+\\dfrac {3} {5} x =80$<br\/>V\u1eady \u0111\u00e1p \u00e1n B \u0111\u00fang<br\/><b>Tr\u01b0\u1eddng h\u1ee3p 3: <\/b> G\u1ecdi s\u1ed1 b\u00e9 l\u00e0 $x\\,\\,(x\\in\\mathbb N^*)$<br\/>V\u00ec hai s\u1ed1 c\u00f3 t\u1ec9 s\u1ed1 l\u00e0 $\\dfrac {3}{5}$ n\u00ean s\u1ed1 l\u1edbn b\u1eb1ng $\\dfrac {5}{3}$ s\u1ed1 b\u00e9 hay s\u1ed1 l\u1edbn l\u00e0 $\\dfrac {5}{3}x$. <br\/>Ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $x+\\dfrac {5} {3} x =80$<br\/>V\u1eady \u0111\u00e1p \u00e1n D \u0111\u00fang<br\/><span class='basic_pink'>Do v\u1eady c\u00e1c \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A,B, D v\u00e0 E.<\/span><br\/><span class='basic_green'>Nh\u1eadn x\u00e9t: <\/span>V\u1edbi b\u00e0i to\u00e1n gi\u1ea3i b\u00e0i to\u00e1n b\u1eb1ng c\u00e1ch l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh, t\u00f9y v\u00e0o d\u1eef ki\u1ec7n c\u1ee7a b\u00e0i to\u00e1n ch\u00fang ta s\u1ebd t\u00ecm \u0111\u01b0\u1ee3c nh\u1eefng bi\u1ec3u th\u1ee9c li\u1ec7n h\u1ec7 kh\u00e1c nhau ph\u1ee5 thu\u1ed9c v\u00e0o \u1ea9n v\u00e0 \u0111\u1ea1i l\u01b0\u1ee3ng \u0111\u00e3 bi\u1ebft. Do v\u1eady, khi l\u00e0m b\u00e0i c\u1ea7n c\u00e2n nh\u1eafc l\u1ef1a ch\u1ecdn nh\u1eefng d\u1eef ki\u1ec7n m\u00e0 ta c\u00f3 th\u1ec3 d\u1ec5 d\u00e0ng t\u00ecm \u0111\u01b0\u1ee3c nhi\u1ec1u m\u1ed1i li\u00ean h\u1ec7 v\u1edbi \u1ea9n s\u1ed1 nh\u1ea5t.<br\/><i>V\u00ed d\u1ee5 nh\u01b0 trong b\u00e0i to\u00e1n n\u00e0y: <\/i> Vi\u1ec7c d\u1ef1a v\u00e0o t\u1ed5ng hai s\u1ed1 s\u1ebd gi\u00fap l\u1eadp \u0111\u01b0\u1ee3c ph\u01b0\u01a1ng tr\u00ecnh d\u1ec5 h\u01a1n v\u00e0 tr\u00e1nh \u0111\u01b0\u1ee3c nh\u1eefng nh\u1ea7m l\u1eabn v\u1ec1 l\u1eddi gi\u1ea3i. <\/span>"}]}],"id_ques":944},{"time":24,"part":[{"time":3,"title":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/5.jpg' \/><\/center>M\u1ed9t h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chu vi l\u00e0 $52 \\,cm$. Bi\u1ebft chi\u1ec1u r\u1ed9ng b\u1eb1ng $\\dfrac 5 8 $ chi\u1ec1u d\u00e0i. T\u00ednh chi\u1ec1u d\u00e0i c\u1ee7a h\u00ecnh ch\u1eef nh\u1eadt.","title_trans":"S\u1eafp x\u1ebfp c\u00e1c b\u01b0\u1edbc gi\u1ea3i to\u00e1n sau \u0111\u1ec3 \u0111\u01b0\u1ee3c m\u1ed9t b\u00e0i gi\u1ea3i ho\u00e0n ch\u1ec9nh c\u1ee7a b\u00e0i to\u00e1n tr\u00ean.","temp":"sequence","correct":[[[3],[2],[4],[1],[5]]],"list":[{"point":5,"image":"","left":["V\u00ec h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chu vi l\u00e0 $52 \\,cm$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $(x+\\dfrac {5} {8} x ).2 =52.$","L\u1ea1i c\u00f3, chi\u1ec1u r\u1ed9ng b\u1eb1ng $\\dfrac 5 8$ chi\u1ec1u d\u00e0i n\u00ean c\u00f3 chi\u1ec1u r\u1ed9ng l\u00e0 $\\dfrac {5} {8} x$ $(cm)$","Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: <br\/>$\\left(x+\\dfrac {5} {8} x \\right).2 =52 \\Leftrightarrow x+\\dfrac {5}{8}x=26 \\Leftrightarrow x=16\\,\\,\\text{(th\u1ecfa m\u00e3n)}$","G\u1ecdi chi\u1ec1u d\u00e0i h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 $x$ $(cm, x>0)$","V\u1eady chi\u1ec1u d\u00e0i h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 $16\\,cm$"],"top":100,"hint":"","explain":"<span class='basic_left'>G\u1ecdi chi\u1ec1u d\u00e0i h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 $x$ $(cm, x>0)$<br\/>L\u1ea1i c\u00f3, chi\u1ec1u r\u1ed9ng b\u1eb1ng $\\dfrac 5 8$ chi\u1ec1u d\u00e0i n\u00ean c\u00f3 chi\u1ec1u r\u1ed9ng l\u00e0 $\\dfrac {5} {8} x$ $(cm)$<br\/>V\u00ec h\u00ecnh ch\u1eef nh\u1eadt c\u00f3 chu vi l\u00e0 $52 \\,cm$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $\\left(x+\\dfrac {5} {8} x \\right).2 =52.$<br\/>Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\left(x+\\dfrac {5} {8} x \\right).2 =52\\\\ \\Leftrightarrow x=16\\,\\,\\text{(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady chi\u1ec1u d\u00e0i h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 $16\\,cm$<br\/><span class='basic_green'>Ghi nh\u1edb: <\/span>C\u00e1c b\u01b0\u1edbc gi\u1ea3i b\u00e0i to\u00e1n b\u1eb1ng c\u00e1ch l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh:<br\/>1. L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh.<br\/>- Ch\u1ecdn \u1ea9n v\u00e0 \u0111\u1eb7t \u0111i\u1ec1u ki\u1ec7n <br\/>- Bi\u1ec3u di\u1ec5n c\u00e1c \u0111\u1ea1i l\u01b0\u1ee3ng ch\u01b0a bi\u1ebft theo \u1ea9n v\u00e0 c\u00e1c \u0111\u1ea1i l\u01b0\u1ee3ng \u0111\u00e3 bi\u1ebft.<br\/>- L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh bi\u1ec3u th\u1ecb m\u1ed1i quan h\u1ec7 gi\u1eefa c\u00e1c \u0111\u1ea1i l\u01b0\u1ee3ng.<br\/>2. Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh.<br\/>3. Ch\u1ecdn c\u00e1c nghi\u1ec7m th\u1ecfa m\u00e3n \u0111i\u1ec1u ki\u1ec7n c\u1ee7a ph\u01b0\u01a1ng tr\u00ecnh r\u1ed3i k\u1ebft lu\u1eadn.<\/span>"}]}],"id_ques":945},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/14h.jpg' \/><\/center><span class='basic_left'>M\u1ed9t h\u00ecnh tam gi\u00e1c c\u00f3 di\u1ec7n t\u00edch b\u1eb1ng $18\\, cm^2$. Bi\u1ebft \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao d\u00e0i h\u01a1n \u0111\u1ed9 d\u00e0i \u0111\u00e1y l\u00e0 $5 \\,cm$. T\u00ednh \u0111\u1ed9 d\u00e0i \u0111\u00e1y h\u00ecnh tam gi\u00e1c.<br\/>G\u1ecdi \u0111\u1ed9 d\u00e0i \u0111\u00e1y h\u00ecnh tam gi\u00e1c l\u00e0 $x$ ($cm$). Ph\u01b0\u01a1ng tr\u00ecnh bi\u1ec3u th\u1ecb b\u00e0i to\u00e1n t\u00ecm \u0111\u1ed9 d\u00e0i \u0111\u00e1y l\u00e0:<\/span>","select":["A. $\\dfrac{x(x+5)}{2}=18$","B. $\\dfrac{x+(x+5)}{2}=18$","C. $[x+(x+5)].2=18$","D. $x(x+5)=18$"],"hint":"S\u1eed d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch tam gi\u00e1c khi bi\u1ebft \u0111\u1ed9 d\u00e0i m\u1ed9t \u0111\u00e1y v\u00e0 chi\u1ec1u cao t\u01b0\u01a1ng \u1ee9ng.","explain":" <span class='basic_left'> G\u1ecdi \u0111\u1ed9 d\u00e0i \u0111\u00e1y tam gi\u00e1c l\u00e0 $x \\,\\,(cm, x>0)$<br\/>V\u00ec \u0111\u1ed9 d\u00e0i \u0111\u01b0\u1eddng cao d\u00e0i h\u01a1n \u0111\u1ed9 d\u00e0i \u0111\u00e1y $5 \\,cm$ n\u00ean ta c\u00f3 chi\u1ec1u cao $x+ 5\\,\\,(cm)$<br\/>V\u00ec di\u1ec7n t\u00edch h\u00ecnh ch\u1eef nh\u1eadt l\u00e0 $18 \\,cm^2$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\dfrac{x(x+5)}{2}=18$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span><br\/><b>Ch\u00fa \u00fd:<\/b> Trong b\u00e0i to\u00e1n gi\u1ea3i b\u00e0i to\u00e1n b\u1eb1ng c\u00e1ch l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh, khi \u0111\u1eb7t \u1ea9n lu\u00f4n ch\u00fa \u00fd \u0111\u1ebfn \u0111i\u1ec1u ki\u1ec7n v\u00e0 \u0111\u01a1n v\u1ecb c\u1ee7a \u1ea9n.<\/span>","column":2}]}],"id_ques":946},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/16.jpg' \/><\/center><span class='basic_left'>Trong d\u1ecbp l\u1ec5 m\u00f9ng $8\/3$. C\u00e1c b\u1ea1n nam l\u1edbp $8B$ c\u00f9ng ra ch\u1ee3 mua $15$ b\u00f4ng h\u1ed3ng v\u00e0 $20$ b\u00f4ng h\u01b0\u1edbng d\u01b0\u01a1ng v\u1ec1 t\u1eb7ng c\u00e1c b\u1ea1n n\u1eef. Bi\u1ebft gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng h\u1ed3ng \u00edt h\u01a1n m\u1ed9t b\u00f4ng h\u01b0\u01a1ng d\u01b0\u01a1ng l\u00e0 $5000$ \u0111\u1ed3ng. C\u00e1c b\u1ea1n mua h\u1ebft $275 000$ \u0111\u1ed3ng. <br\/>G\u1ecdi gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng h\u1ed3ng l\u00e0 $x$ (\u0111\u1ed3ng, $x\\in\\mathbb N^*$). Ph\u01b0\u01a1ng tr\u00ecnh bi\u1ec3u th\u1ecb b\u00e0i to\u00e1n t\u00ednh gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng h\u1ed3ng l\u00e0:<\/span> ","select":["A. $15x+20(x-5000)=275000$","B. $15x+20(x+5000)=275000$","C. $20x+15(x+5000)=275000$","D. $20x+15(x-5000)=275000$"],"hint":"T\u1eeb gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng h\u1ed3ng, suy ra gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng hoa h\u01b0\u1edbng d\u01b0\u01a1ng v\u00e0 l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh","explain":"<span class='basic_left'>G\u1ecdi gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng h\u1ed3ng l\u00e0 $x$ (\u0111\u1ed3ng, $x>0$)<br\/>Gi\u00e1 ti\u1ec1n mua $15$ b\u00f4ng h\u1ed3ng l\u00e0 $15x$ (\u0111\u1ed3ng)<br\/>Gi\u00e1 ti\u1ec1n m\u1ed9t b\u00f4ng h\u01b0\u1edbng d\u01b0\u01a1ng l\u00e0 $x+5000$ (\u0111\u1ed3ng).<br\/>Gi\u00e1 ti\u1ec1n mua $20$ b\u00f4ng hoa h\u01b0\u1edbng d\u01b0\u01a1ng l\u00e0 $20(x+5000)$ (\u0111\u1ed3ng)<br\/>V\u00ec c\u00e1c b\u1ea1n nam mua $15$ b\u00f4ng h\u1ed3ng v\u00e0 $20$ b\u00f4ng h\u01b0\u1edbng d\u01b0\u01a1ng h\u1ebft $275000$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$15x+20(x+5000)=275000$.<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span><\/span>","column":2}]}],"id_ques":947},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["43"]]],"list":[{"point":5,"width":50,"type_input":"","input_hint":"frac","ques":"<span class='basic_left'>Nh\u00e0 b\u00e0 Th\u1ea3o \u1edf qu\u00ea c\u00f3 nu\u00f4i l\u1ee3n v\u00e0 g\u00e0. Th\u1ea3o ngh\u0129 ra m\u1ed9t b\u00e0i to\u00e1n \u0111\u1ec3 \u0111\u1ed1 b\u1ea1n H\u00e0: \u201c Nh\u00e0 b\u00e0 m\u00ecnh c\u00f3 nu\u00f4i g\u00e0 v\u00e0 l\u1ee3n. Bi\u1ebft s\u1ed1 g\u00e0 \u00edt h\u01a1n s\u1ed1 l\u1ee3n l\u00e0 $12$ con v\u00e0 t\u1ed5ng s\u1ed1 g\u00e0 v\u00e0 l\u1ee3n nh\u00e0 b\u00e0 m\u00ecnh b\u1eb1ng s\u1ed1 ch\u1eb5n l\u1edbn nh\u1ea5t c\u00f3 hai ch\u1eef s\u1ed1. V\u1eady \u0111\u1ed1 b\u1ea1n nh\u00e0 b\u00e0 m\u00ecnh c\u00f3 bao nhi\u00eau con g\u00e0?\u201d H\u00e0 d\u1ec5 d\u00e0ng t\u00ecm \u0111\u01b0\u1ee3c \u0111\u00e1p \u00e1n.<br\/>Theo b\u1ea1n, nh\u00e0 b\u00e0 Th\u1ea3o c\u00f3 bao nhi\u00eau con g\u00e0?<br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_(con)<\/span> ","hint":"G\u1ecdi s\u1ed1 g\u00e0 l\u00e0 \u1ea9n s\u1ed1.","explain":"<span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi s\u1ed1 con g\u00e0 l\u00e0 \u1ea9n<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n s\u1ed1 con l\u1ee3n theo \u1ea9n<br\/><b>B\u01b0\u1edbc 3:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh <br\/><b>B\u01b0\u1edbc 4:<\/b> Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh r\u1ed3i k\u1ebft lu\u1eadn<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi s\u1ed1 g\u00e0 nh\u00e0 b\u00e0 Th\u1ea3o nu\u00f4i l\u00e0 $x$ (con, $x\\in\\mathbb N^*$)<br\/>V\u00ec s\u1ed1 g\u00e0 \u00edt h\u01a1n s\u1ed1 l\u1ee3n l\u00e0 $12$ con n\u00ean s\u1ed1 l\u1ee3n nh\u00e0 b\u00e0 Th\u1ea3o nu\u00f4i l\u00e0 $x+12$ (con)<br\/>T\u1ed5ng s\u1ed1 g\u00e0 v\u00e0 s\u1ed1 l\u1ee3n l\u00e0 s\u1ed1 ch\u1eb5n l\u1edbn nh\u1ea5t c\u00f3 hai ch\u1eef s\u1ed1 t\u1ee9c c\u00f3 $98$ con.<br\/>Ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $x+x+12=98$<br\/>Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: <br\/>$x+x+12=98\\\\ \\Leftrightarrow 2x=86 \\\\ \\Leftrightarrow x=43\\,\\,\\,\\text {(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady nh\u00e0 b\u00e0 Th\u1ea3o nu\u00f4i $43$ con g\u00e0.<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $43$<\/span><br\/><b> Ch\u00fa \u00fd: <\/b> Khi tr\u00ecnh b\u00e0y b\u00e0i to\u00e1n gi\u1ea3i b\u00e0i to\u00e1n b\u1eb1ng c\u00e1ch l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh, m\u1ed7i bi\u1ec3u th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa \u1ea9n v\u00e0 c\u00e1c \u0111\u1ea1i l\u01b0\u1ee3ng kh\u00e1c c\u1ea7n gi\u1ea3i th\u00edch r\u00f5 r\u00e0ng v\u00e0 k\u00e8m theo \u0111\u01a1n v\u1ecb \u0111\u1ec3 b\u00e0i to\u00e1n \u0111\u01b0\u1ee3c logic v\u00e0 ch\u1eb7t ch\u1ebd. <\/span>"}]}],"id_ques":948},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["23"],["31"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<span class='basic_left'>B\u1ea1n H\u00e0 c\u0169ng \u0111\u1ed1 l\u1ea1i b\u1ea1n Th\u1ea3o: \u201c\u00d4ng m\u00ecnh \u1edf qu\u00ea c\u0169ng nu\u00f4i b\u00f2 v\u00e0 v\u1ecbt. \u00d4ng b\u1ea3o, \u00f4ng c\u00f3 t\u1ed5ng c\u1ed9ng $54$ con c\u1ea3 b\u00f2 v\u00e0 v\u1ecbt v\u00e0 t\u1ea5t c\u1ea3 c\u00f3 $154$ ch\u00e2n. \u0110\u1ed1 b\u1ea1n \u00f4ng m\u00ecnh nu\u00f4i bao nhi\u00eau con b\u00f2 v\u00e0 bao nhi\u00eau con v\u1ecbt?\u201d Th\u1ea3o c\u0169ng \u0111\u00e3 tr\u1ea3 l\u1eddi \u0111\u00fang.<br\/>Theo b\u1ea1n, nh\u00e0 \u00f4ng H\u00e0 c\u00f3 bao nhi\u00eau con b\u00f2 v\u00e0 bao nhi\u00eau con v\u1ecbt?<br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_(con b\u00f2);_input_(con v\u1ecbt)<\/span> ","hint":"L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh d\u1ef1a theo m\u1ed1i li\u00ean h\u1ec7 v\u1ec1 s\u1ed1 ch\u00e2n c\u1ee7a hai con v\u1eadt.","explain":"<span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi s\u1ed1 b\u00f2 (ho\u1eb7c v\u1ecbt) l\u00e0 \u1ea9n<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n s\u1ed1 con v\u1ecbt (ho\u1eb7c b\u00f2) theo \u1ea9n<br\/><b>B\u01b0\u1edbc 3:<\/b> Bi\u1ec3u di\u1ec5n s\u1ed1 ch\u00e2n m\u1ed7i con theo \u1ea9n.<br\/><b>B\u01b0\u1edbc 4:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh <br\/>B\u01b0\u1edbc 5: Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh r\u1ed3i k\u1ebft lu\u1eadn<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi s\u1ed1 b\u00f2 nh\u00e0 \u00f4ng H\u00e0 nu\u00f4i l\u00e0 $x$ (con, $x\\in\\mathbb N^*$)<br\/>B\u00f2 c\u00f3 $4$ ch\u00e2n n\u00ean t\u1ed5ng s\u1ed1 ch\u00e2n b\u00f2 l\u00e0 $4x$ (ch\u00e2n)<br\/>V\u00ec \u00f4ng c\u00f3 t\u1ed5ng c\u1ed9ng $54$ con c\u1ea3 b\u00f2 v\u00e0 v\u1ecbt n\u00ean s\u1ed1 con v\u1ecbt nh\u00e0 \u00f4ng H\u00e0 nu\u00f4i l\u00e0 $54-x$ (con)<br\/>V\u1ecbt c\u00f3 $2$ ch\u00e2n n\u00ean t\u1ed5ng s\u1ed1 ch\u00e2n v\u1ecbt l\u00e0 $2(54-x)$ (ch\u00e2n)<br\/>V\u00ec t\u1ed5ng s\u1ed1 ch\u00e2n l\u00e0 $154$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $4x+2(54-x)=154$<br\/>Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: <br\/>$4x+2(54-x)=154\\\\ \\Leftrightarrow 2x+108=154\\\\ \\Leftrightarrow 2x=46 \\\\ \\Leftrightarrow x=23\\,\\,\\,\\text {(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady nh\u00e0 \u00f4ng H\u00e0 nu\u00f4i $23$ con b\u00f2 v\u00e0 $54-23=31$ con v\u1ecbt<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u1ea7n l\u01b0\u1ee3t l\u00e0 $23$ v\u00e0 $31$<\/span><br\/><b>Nh\u1eadn x\u00e9t: <\/b>B\u00e0i to\u00e1n c\u0169ng c\u00f3 th\u1ec3 th\u1ef1c hi\u1ec7n b\u1eb1ng c\u00e1ch g\u1ecdi s\u1ed1 v\u1ecbt l\u00e0 $x$ (con, $x\\in\\mathbb N^*$).<br\/>Khi \u0111\u00f3 ta s\u1ebd c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh d\u1ea1ng: $2x+4(54-x)=154$ <br\/>V\u00e0 c\u0169ng gi\u1ea3i ra \u0111\u01b0\u1ee3c \u0111\u00e1p \u00e1n nh\u01b0 b\u00e0i gi\u1ea3i tr\u00ean.<br\/>V\u1edbi b\u00e0i to\u00e1n gi\u1ea3i b\u00e0i to\u00e1n b\u1eb1ng c\u00e1ch l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh, t\u00f9y thu\u1ed9c v\u00e0o c\u00e1ch g\u1ecdi \u1ea9n s\u1ebd cho ta m\u1ed9t ph\u01b0\u01a1ng tr\u00ecnh kh\u00e1c nhau.<br\/>V\u00ec v\u1eady khi g\u1ecdi \u1ea9n n\u00ean c\u00e2n nh\u1eafc l\u1ef1a ch\u1ecdn \u0111\u1ea1i l\u01b0\u1ee3ng n\u00e0o l\u00e0m \u1ea9n \u0111\u1ec3 thu \u0111\u01b0\u1ee3c ph\u01b0\u01a1ng tr\u00ecnh d\u1ec5 d\u00e0ng v\u00e0 d\u1ec5 gi\u1ea3i nh\u1ea5t c\u00f3 th\u1ec3.<\/span>"}]}],"id_ques":949},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"M\u1ed9t ng\u01b0\u1eddi \u0111i xe m\u00e1y t\u1eeb $A$ \u0111\u1ebfn $B$ v\u1edbi v\u1eadn t\u1ed1c $30 km\/h$. L\u00fac v\u1ec1 ng\u01b0\u1eddi n\u00e0y \u0111i v\u1edbi v\u1eadn t\u1ed1c $24 km\/ h$. Do \u0111\u00f3 th\u1eddi gian v\u1ec1 l\u00e2u h\u01a1n th\u1eddi gian \u0111i l\u00e0 $30$ ph\u00fat. T\u00ednh qu\u00e3ng \u0111\u01b0\u1eddng $AB$. <br\/>G\u1ecdi qu\u00e3ng \u0111\u01b0\u1eddng $AB$ l\u00e0 $x\\, (km)$ th\u00ec ph\u01b0\u01a1ng tr\u00ecnh c\u1ee7a b\u00e0i to\u00e1n l\u00e0: ","select":["A. $\\dfrac {x}{24}-\\dfrac{x}{30}=30$","B. $\\dfrac {x}{30}-\\dfrac{x}{24}=30$","C. $\\dfrac {x}{30}-\\dfrac{x}{24}=\\dfrac {1}{2}$","D. $\\dfrac {x}{24}-\\dfrac{x}{30}=\\dfrac {1}{2}$"],"hint":"S\u1eed d\u1ee5ng c\u00f4ng th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa v\u1eadn t\u1ed1c, qu\u00e3ng \u0111\u01b0\u1eddng v\u00e0 th\u1eddi gian.<br\/>Bi\u1ec3u di\u1ec5n th\u1eddi gian c\u1ee7a ng\u01b0\u1eddi \u0111i xe m\u00e1y l\u00fac \u0111i v\u00e0 v\u1ec1.","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng $AB$ l\u00e0 \u1ea9n<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n th\u1eddi gian \u0111i v\u00e0 v\u1ec1 theo \u1ea9n<br\/><b>B\u01b0\u1edbc 3:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh t\u1eeb gi\u1ea3 thi\u1ebft<br\/><b>B\u01b0\u1edbc 4:<\/b> Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh v\u00e0 k\u1ebft lu\u1eadn.<br\/>L\u1eadp b\u1ea3ng:<br\/><br\/><table><tr><th><\/th><th>Qu\u00e3ng \u0111\u01b0\u1eddng($km$)<\/th><th>V\u1eadn t\u1ed1c($km\/h$)<\/th><th>Th\u1eddi gian (gi\u1edd)<\/th><\/tr><tr><td>T\u1eeb $A$ \u0111\u1ebfn $B$<\/td><td>$x$<\/td><td>$30$<\/td><td>$\\dfrac {x}{30}$<\/td><\/tr><tr><td>T\u1eeb $B$ v\u1ec1 $A$<\/td><td>$x$<\/td><td>$24$<\/td><td>$\\dfrac {x}{20}$<\/td><\/tr><\/table><br\/><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi qu\u00e3ng \u0111\u01b0\u1eddng $AB$ l\u00e0 $x$ ($km,\\,x > 0$)<br\/>V\u00ec ng\u01b0\u1eddi \u0111i xe m\u00e1y t\u1eeb $A$ \u0111\u1ebfn $B$ v\u1edbi v\u1eadn t\u1ed1c $30 km\/h$ n\u00ean th\u1eddi gian \u0111i l\u00e0 $\\dfrac {x}{30}$ (gi\u1edd)<br\/>V\u00ec l\u00fac v\u1ec1 ng\u01b0\u1eddi n\u00e0y \u0111i v\u1edbi v\u1eadn t\u1ed1c $24 km\/ h$ n\u00ean th\u1eddi gian v\u1ec1 l\u00e0 $\\dfrac {x}{24}$ (gi\u1edd)<br\/>V\u00ec th\u1eddi gian v\u1ec1 l\u00e2u h\u01a1n th\u1eddi gian \u0111i l\u00e0 $30$ ph\u00fat $=\\dfrac {1}{2}$ (gi\u1edd) n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\dfrac {x}{24}-\\dfrac{x}{30}=\\dfrac {1}{2}$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D <\/span><br\/><b>Ghi nh\u1edb:<\/b><br\/>- \u0110\u1ed1i v\u1edbi b\u00e0i to\u00e1n chuy\u1ec3n \u0111\u1ed9ng, lu\u00f4n th\u1ed1ng nh\u1ea5t c\u00e1c \u0111\u01a1n v\u1ecb \u0111o c\u1ee7a c\u00e1c \u0111\u1ea1i l\u01b0\u1ee3ng: Qu\u00e3ng \u0111\u01b0\u1eddng ($km$), v\u1eadn t\u1ed1c ($km\/h$) v\u00e0 th\u1eddi gian (gi\u1edd)<br\/>Do v\u1eady, khi \u0111\u1ec1 b\u00e0i cho th\u1eddi gian l\u00e0 ph\u00fat lu\u00f4n c\u00f3 m\u1ed9t b\u01b0\u1edbc \u0111\u1ed5i \u0111\u01a1n v\u1ecb th\u1eddi gian sang gi\u1edd.<\/span>","column":2}]}],"id_ques":950},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["105"]]],"list":[{"point":5,"width":50,"type_input":"","input_hint":"","ques":"<span class='basic_left'>M\u1ed9t ng\u01b0\u1eddi \u0111i t\u1eeb $A$ \u0111\u1ebfn $B$ v\u1edbi v\u1eadn t\u1ed1c $35$ $km\/h$. Khi v\u1ec1, ng\u01b0\u1eddi \u0111\u00f3 t\u0103ng v\u1eadn t\u1ed1c th\u00eam $7\\,km\/h$ th\u00ec th\u1eddi gian v\u1ec1 \u00edt h\u01a1n th\u1eddi gian \u0111i l\u00e0 $30$ ph\u00fat. T\u00ednh qu\u00e3ng \u0111\u01b0\u1eddng $AB$.<br\/><b>\u0110\u00e1p s\u1ed1: <\/b>$AB=$ _input_$(km)$<\/span>","hint":"S\u1eed d\u1ee5ng c\u00f4ng th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa v\u1eadn t\u1ed1c, qu\u00e3ng \u0111\u01b0\u1eddng v\u00e0 th\u1eddi gian.","explain":"<span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng $AB$ l\u00e0 \u1ea9n<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n th\u1eddi gian \u0111i v\u00e0 th\u1eddi gian v\u1ec1 theo \u1ea9n<br\/><b>B\u01b0\u1edbc 3:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh<br\/><b>B\u01b0\u1edbc 4:<\/b> Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh r\u1ed3i k\u1ebft lu\u1eadn<br\/>L\u1eadp b\u1ea3ng:<br\/><table><tr><th><\/th><th>Qu\u00e3ng \u0111\u01b0\u1eddng($km$)<\/th><th>V\u1eadn t\u1ed1c($km\/h$)<\/th><th>Th\u1eddi gian (gi\u1edd)<\/th><\/tr><tr><td>T\u1eeb $A$ \u0111\u1ebfn $B$<\/td><td>$x$<\/td><td>$35$<\/td><td>$\\dfrac {x}{35}$<\/td><\/tr><tr><td>T\u1eeb $B$ v\u1ec1 $A$<\/td><td>$x$<\/td><td>$35+7=42$<\/td><td>$\\dfrac {x}{42}$<\/td><\/tr><\/table><br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng $AB$ l\u00e0 $x$ $(km, x>0)$ <br\/>Ng\u01b0\u1eddi \u0111\u00f3 \u0111i t\u1eeb $A$ \u0111\u1ebfn $B$ v\u1edbi v\u1eadn t\u1ed1c $35\\,km\/h$ n\u00ean th\u1eddi gian \u0111i l\u00e0 $\\dfrac {x}{35}$ (gi\u1edd)<br\/>Khi v\u1ec1 ng\u01b0\u1eddi \u0111\u00f3 t\u0103ng v\u1eadn t\u1ed1c th\u00eam $7\\,km\/h$ n\u00ean v\u1eadn t\u1ed1c v\u1ec1 l\u00e0 $35+7=42 \\,( km\/h)$<br\/>Th\u1eddi gian ng\u01b0\u1eddi \u0111\u00f3 \u0111i t\u1eeb $B$ v\u1ec1 $A$ l\u00e0: $\\dfrac {x}{42}$ (gi\u1edd)<br\/>Th\u1eddi gian v\u1ec1 \u00edt h\u01a1n th\u1eddi gian \u0111i $30$ ph\u00fat $=\\dfrac {1}{2}$ gi\u1edd n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $\\dfrac {x}{35}-\\dfrac {x}{42}=\\dfrac {1}{2}$<br\/>Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh: <br\/>$\\dfrac {x}{35}-\\dfrac {x}{42}=\\dfrac {1}{2}\\\\ \\Leftrightarrow \\dfrac {6x}{210}-\\dfrac {5x}{210}=\\dfrac {105}{210}\\\\ \\Leftrightarrow 6x-5x=105\\\\ \\Leftrightarrow x=105\\,\\,\\,\\text {(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady qu\u00e3ng \u0111\u01b0\u1eddng $AB$ d\u00e0i $105 \\,km$<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $105$<\/span><br\/><b>Sai l\u1ea7m th\u01b0\u1eddng g\u1eb7p:<\/b> H\u1ecdc sinh th\u01b0\u1eddng qu\u00ean kh\u00f4ng \u0111\u1ed5i \u0111\u01a1n v\u1ecb th\u1eddi gian d\u1eabn \u0111\u1ebfn l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh sai v\u00e0 kh\u00f4ng t\u00ecm \u0111\u01b0\u1ee3c \u0111\u00e1p s\u1ed1 c\u1ee7a b\u00e0i to\u00e1n.<\/span>"}]}],"id_ques":951},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["10"]]],"list":[{"point":5,"width":50,"type_input":"","input_hint":"","ques":"<span class='basic_left'>B\u00e1c An \u0111i t\u1eeb nh\u00e0 l\u00ean t\u1ec9nh v\u1edbi v\u1eadn t\u1ed1c $20km\/h$ r\u1ed3i l\u00e0m vi\u1ec7c tr\u00ean \u0111\u00f3 m\u1ea5t $1$ gi\u1edd $30$ ph\u00fat. B\u00e1c v\u1ec1 nh\u00e0 v\u1edbi v\u1eadn t\u1ed1c l\u00e0 $25 km$. T\u1ed5ng th\u1eddi gian c\u1ea3 \u0111i, l\u00e0m vi\u1ec7c v\u00e0 v\u1ec1 l\u00e0 $2$ gi\u1edd $24$ ph\u00fat. H\u1ecfi qu\u00e3ng \u0111\u01b0\u1eddng t\u1eeb nh\u00e0 l\u00ean t\u1ec9nh c\u1ee7a b\u00e1c An d\u00e0i bao nhi\u00eau $km$?<br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_$(km)$<\/span>","hint":"S\u1eed d\u1ee5ng c\u00f4ng th\u1ee9c li\u00ean h\u1ec7 gi\u1eefa v\u1eadn t\u1ed1c, qu\u00e3ng \u0111\u01b0\u1eddng v\u00e0 th\u1eddi gian.","explain":"<span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng t\u1eeb nh\u00e0 l\u00ean t\u1ec9nh l\u00e0 \u1ea9n.<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n th\u1eddi gian \u0111i v\u00e0 th\u1eddi gian v\u1ec1 theo \u1ea9n<br\/><b>B\u01b0\u1edbc 3:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh<br\/><b>B\u01b0\u1edbc 4:<\/b> Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh r\u1ed3i k\u1ebft lu\u1eadn<br\/>L\u1eadp b\u1ea3ng:<br\/><table><tr><th><\/th><th>Qu\u00e3ng \u0111\u01b0\u1eddng ($km$)<\/th><th>V\u1eadn t\u1ed1c($km\/h$)<\/th><th>Th\u1eddi gian<\/th><\/tr><tr><td>\u0110i t\u1eeb nh\u00e0 l\u00ean t\u00ecnh<\/td><td>$x$<\/td><td>$20$<\/td><td>$\\dfrac {x}{20}$<\/td><\/tr><tr><td>L\u00e0m vi\u1ec7c tr\u00ean t\u1ec9nh<\/td><td>$0$<\/td><td>$0$<\/td><td>$1$ gi\u1edd $30$ ph\u00fat $=\\dfrac {3}{2}$ gi\u1edd<\/td><\/tr><tr><td>\u0110i t\u1eeb t\u1ec9nh v\u1ec1 nh\u00e0<\/td><td>$x$<\/td><td>$25$<\/td><td>$\\dfrac {x}{25}$<\/td><\/tr><\/table><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng m\u00e0 b\u00e1c An l\u00ean t\u1ec9nh l\u00e0 $x$ $(km, x>0)$ <br\/>V\u00ec b\u00e1c \u0111i l\u00ean t\u1ec9nh v\u1edbi v\u1eadn t\u1ed1c l\u00e0 $20\\,km\/h$ n\u00ean th\u1eddi gian \u0111i l\u00e0 $\\dfrac {x}{20}$ gi\u1edd. <br\/>Th\u1eddi gian b\u00e1c l\u00e0m vi\u1ec7c l\u00e0 $1$ gi\u1edd $30$ ph\u00fat $=\\dfrac {3}{2}$ gi\u1edd.<br\/>Th\u1eddi gian b\u00e1c v\u1ec1 v\u1edbi v\u1eadn t\u1ed1c $25\\,km\/h$ l\u00e0 $\\dfrac {x}{25}$ gi\u1edd.<br\/>V\u00ec t\u1ed5ng th\u1eddi gian c\u1ea3 \u0111i, l\u00e0m vi\u1ec7c v\u00e0 v\u1ec1 l\u00e0 $2$ gi\u1edd $24$ ph\u00fat $=\\dfrac {12}{5}$ gi\u1edd n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\dfrac {x}{20}+\\dfrac {3}{2}+\\dfrac {x}{25}=\\dfrac {12}{5}\\\\ \\Leftrightarrow \\dfrac {x}{20}+\\dfrac {x}{25}=\\dfrac {9}{10}\\\\ \\Leftrightarrow 5x+4x=90\\\\ \\Leftrightarrow x=10\\,\\,\\,\\text{(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady qu\u00e3ng \u0111\u01b0\u1eddng t\u1eeb nh\u00e0 l\u00ean t\u1ec9nh c\u1ee7a b\u00e1c An l\u00e0 $10\\,km$<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $10$<\/span><br\/><span class='basic_green'>Sai l\u1ea7m th\u01b0\u1eddng g\u1eb7p:<\/span> H\u1ecdc sinh th\u01b0\u1eddng qu\u00ean kh\u00f4ng \u0111\u1ed5i \u0111\u01a1n v\u1ecb th\u1eddi gian d\u1eabn \u0111\u1ebfn l\u1eadp ph\u01b0\u01a1ng tr\u00ecnh sai v\u00e0 kh\u00f4ng t\u00ecm \u0111\u01b0\u1ee3c \u0111\u00e1p s\u1ed1 c\u1ee7a b\u00e0i to\u00e1n.<\/span>"}]}],"id_ques":952},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/9.jpg' \/><\/center><span class='basic_left'>Trong ba ng\u00e0y l\u00e0m vi\u1ec7c, $2$ ng\u01b0\u1eddi l\u00e0m \u0111\u01b0\u1ee3c $930$ s\u1ea3n ph\u1ea9m. Bi\u1ebft m\u1ed7i ng\u00e0y, ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m nhi\u1ec1u h\u01a1n ng\u01b0\u1eddi th\u1ee9 hai $10$ s\u1ea3n ph\u1ea9m. H\u1ecfi m\u1ed7i ng\u00e0y, ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m \u0111\u01b0\u1ee3c bao nhi\u00eau s\u1ea3n ph\u1ea9m?<\/span>","select":["A. $160$ s\u1ea3n ph\u1ea9m","B. $150$ s\u1ea3n ph\u1ea9m","C. $470$ s\u1ea3n ph\u1ea9m","D. $460$ s\u1ea3n ph\u1ea9m"],"hint":"G\u1ecdi s\u1ed1 s\u1ea3n ph\u1ea9m ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m trong m\u1ed9t ng\u00e0y l\u00e0 $x$ (s\u1ea3n ph\u1ea9m)","explain":" <span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi s\u1ed1 s\u1ea3n ph\u1ea9m ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m l\u00e0 \u1ea9n.<br\/><b>B\u01b0\u1edbc 2:<\/b> Bi\u1ec3u di\u1ec5n s\u1ed1 s\u1ea3n ph\u1ea9m ng\u01b0\u1eddi th\u1ee9 hai l\u00e0m theo \u1ea9n.<br\/><b>B\u01b0\u1edbc 3:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh<br\/><b>B\u01b0\u1edbc 4:<\/b> Gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh r\u1ed3i k\u1ebft lu\u1eadn<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi s\u1ed1 s\u1ea3n ph\u1ea9m ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m trong m\u1ed9t ng\u00e0y l\u00e0 $x$ (s\u1ea3n ph\u1ea9m,$x\\in\\mathbb N^*$)<br\/>V\u00ec m\u1ed7i ng\u00e0y, ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m nhi\u1ec1u h\u01a1n ng\u01b0\u1eddi th\u1ee9 hai $10$ s\u1ea3n ph\u1ea9m n\u00ean s\u1ed1 s\u1ea3n ph\u1ea9m ng\u01b0\u1eddi th\u1ee9 hai l\u00e0m trong m\u1ed9t ng\u00e0y l\u00e0 $x-10$ (s\u1ea3n ph\u1ea9m)<br\/>Trong ba ng\u00e0y l\u00e0m vi\u1ec7c $2$ ng\u01b0\u1eddi l\u00e0m \u0111\u01b0\u1ee3c $930$ s\u1ea3n ph\u1ea9m n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$3x+3(x-10)=930\\\\ \\Leftrightarrow 6x=960\\\\ \\Leftrightarrow x=160\\,\\,\\,\\text {(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady m\u1ed7i ng\u00e0y ng\u01b0\u1eddi th\u1ee9 nh\u1ea5t l\u00e0m \u0111\u01b0\u1ee3c $160$ s\u1ea3n ph\u1ea9m<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span><\/span>","column":2}]}],"id_ques":953},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["37"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/11.jpg' \/><\/center><span class='basic_left'>T\u00ecm m\u1ed9t s\u1ed1 t\u1ef1 nhi\u00ean c\u00f3 hai ch\u1eef s\u1ed1. Bi\u1ebft t\u1ed5ng hai ch\u1eef s\u1ed1 \u0111\u00f3 l\u00e0 $10$ v\u00e0 n\u1ebfu \u0111\u1ed5i ch\u1ed7 hai ch\u1eef s\u1ed1 th\u00ec \u0111\u01b0\u1ee3c m\u1ed9t s\u1ed1 m\u1edbi l\u1edbn h\u01a1n s\u1ed1 ban \u0111\u1ea7u l\u00e0 $36$ \u0111\u01a1n v\u1ecb.<br\/><b>\u0110\u00e1p s\u1ed1: <\/b> S\u1ed1 \u0111\u00f3 l\u00e0: _input_<\/span>","hint":"G\u1ecdi ch\u1eef s\u1ed1 h\u00e0ng ch\u1ee5c l\u00e0 $x$ ($x\\in\\mathbb N^*,\\, 0 < x < 10$)","explain":"<span class='basic_left'>G\u1ecdi ch\u1eef s\u1ed1 h\u00e0ng ch\u1ee5c l\u00e0 $x$ ($x\\in\\mathbb N^*,\\, 0 < x < 10$) <br\/>V\u00ec t\u1ed5ng hai ch\u1eef s\u1ed1 l\u00e0 $10$ n\u00ean ch\u1eef s\u1ed1 h\u00e0ng \u0111\u01a1n v\u1ecb l\u00e0 $10-x$<br\/>S\u1ed1 t\u1ef1 nhi\u00ean c\u00f3 ch\u1eef s\u1ed1 h\u00e0ng ch\u1ee5c l\u00e0 $x$ v\u00e0 ch\u1eef s\u1ed1 h\u00e0ng \u0111\u01a1n v\u1ecb l\u00e0 $10-x$ c\u00f3 gi\u00e1 tr\u1ecb b\u1eb1ng $\\overline{x(10-x)} =10x+(10-x)$<br\/>Khi \u0111\u1ed5i ch\u1ed7 ch\u1eef s\u1ed1 h\u00e0ng \u0111\u01a1n v\u1ecb v\u00e0 ch\u1eef s\u1ed1 h\u00e0ng ch\u1ee5c ta \u0111\u01b0\u1ee3c s\u1ed1 m\u1edbi l\u00e0: $\\overline{(10-x)x}=10(10-x)+x$<br\/> V\u00ec khi \u0111\u1ed5i ch\u1ed7 hai ch\u1eef s\u1ed1 \u1ea5y th\u00ec \u0111\u01b0\u1ee3c m\u1ed9t s\u1ed1 m\u1edbi l\u1edbn h\u01a1n s\u1ed1 ban \u0111\u1ea7u l\u00e0 $36$ \u0111\u01a1n v\u1ecb n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\begin{align} & \\overline{x(10-x)}+36=\\overline{(10-x)x} \\\\ & \\Leftrightarrow 10x+10-x+36=10(10-x)+x \\\\ & \\Leftrightarrow 9x+46=-9x+100 \\\\ & \\Leftrightarrow 18x=54 \\\\ & \\Leftrightarrow x=3 \\\\ \\end{align}$ <br\/>V\u1eady ch\u1eef s\u1ed1 h\u00e0ng ch\u1ee5c l\u00e0 $3$, suy ra ch\u1eef s\u1ed1 h\u00e0ng \u0111\u01a1n v\u1ecb l\u00e0 $7$. <br\/>Do \u0111\u00f3, s\u1ed1 ph\u1ea3i t\u00ecm l\u00e0 $37$<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $37$<\/span><br\/><b>Ghi nh\u1edb:<\/b> S\u1ed1 c\u00f3 hai ch\u1eef s\u1ed1 c\u00f3 d\u1ea1ng $\\overline {ab}\\,\\,(a\\ne 0)$ c\u00f3 gi\u00e1 tr\u1ecb b\u1eb1ng $10a+b$<\/span>"}]}],"id_ques":954},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/13.jpg' \/><\/center><span class='basic_left'>M\u1ed9t chi\u1ebfc thuy\u1ec1n \u0111i tr\u00ean m\u1ed9t d\u00f2ng s\u00f4ng d\u00e0i $50\\,km$. T\u1ed5ng th\u1eddi gian xu\u00f4i d\u00f2ng v\u00e0 ng\u01b0\u1ee3c d\u00f2ng l\u00e0 $4$ gi\u1edd $10$ ph\u00fat. T\u00ednh v\u1eadn t\u1ed1c c\u1ee7a thuy\u1ec1n bi\u1ebft v\u1eadn t\u1ed1c d\u00f2ng n\u01b0\u1edbc l\u00e0 $5\\,km\/h$.<br\/>G\u1ecdi v\u1eadn t\u1ed1c c\u1ee7a thuy\u1ec1n l\u00e0 $x$ th\u00ec ph\u01b0\u01a1ng tr\u00ecnh bi\u1ec3u th\u1ecb b\u00e0i to\u00e1n t\u00ecm v\u1eadn t\u1ed1c thuy\u1ec1n l\u00e0:<\/span>","select":["A. $\\dfrac {50}{x-5}+\\dfrac {50}{x-5}=\\dfrac {25}{6}$","B. $\\dfrac {50}{x+5}-\\dfrac {50}{x-5}=\\dfrac {25}{6}$","C. $\\dfrac {50}{x+5}+\\dfrac {50}{x-5}=\\dfrac {41}{10}$","D. $\\dfrac {50}{x+5}+\\dfrac {50}{x-5}=\\dfrac {25}{6}$"],"hint":"V\u1eadn t\u1ed1c xu\u00f4i d\u00f2ng $=$ v\u1eadn t\u1ed1c thuy\u1ec1n $+$ v\u1eadn t\u1ed1c d\u00f2ng n\u01b0\u1edbc.<br\/>V\u1eadn t\u1ed1c ng\u01b0\u1ee3c d\u00f2ng $=$ v\u1eadn t\u1ed1c thuy\u1ec1n $-$ v\u1eadn t\u1ed1c d\u00f2ng n\u01b0\u1edbc.","explain":" <span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/><b>B\u01b0\u1edbc 1:<\/b> G\u1ecdi v\u1eadn t\u1ed1c thuy\u1ec1n l\u00e0 \u1ea9n $x$ v\u00e0 bi\u1ec3u di\u1ec5n v\u1eadn t\u1ed1c xu\u00f4i d\u00f2ng v\u00e0 ng\u01b0\u1ee3c d\u00f2ng theo \u1ea9n $x$<br\/><b>B\u01b0\u1edbc 2:<\/b> Vi\u1ebft bi\u1ec3u th\u1ee9c bi\u1ec3u th\u1ecb th\u1eddi gian xu\u00f4ng d\u00f2ng v\u00e0 th\u1eddi gian ng\u01b0\u1ee3c d\u00f2ng.<br\/><b>B\u01b0\u1edbc 3:<\/b> L\u1eadp ph\u01b0\u01a1ng tr\u00ecnh<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>G\u1ecdi v\u1eadn t\u1ed1c thuy\u1ec1n l\u00e0 \u1ea9n $x$ ($km\/h$, $x>0$)<br\/>V\u00ec v\u1eadn t\u1ed1c d\u00f2ng n\u01b0\u1edbc l\u00e0 $5 km\/h$ n\u00ean v\u1eadn t\u1ed1c thuy\u1ec1n khi xu\u00f4i d\u00f2ng l\u00e0 $x+5$ ($km\/h$).<br\/> Do v\u1eady th\u1eddi gian thuy\u1ec1n \u0111i xu\u00f4i d\u00f2ng l\u00e0 $\\dfrac {50}{x+5}$ (gi\u1edd)<br\/>V\u1eadn t\u1ed1c khi thuy\u1ec1n \u0111i ng\u01b0\u1ee3c d\u00f2ng l\u00e0 $x-5$ ($km\/h$).<br\/> Do v\u1eady th\u1eddi gian thuy\u1ec1n \u0111i ng\u01b0\u1ee3c d\u00f2ng l\u00e0 $\\dfrac {50}{x-5}$ (gi\u1edd)<br\/>V\u00ec t\u1ed5ng th\u1eddi gian xu\u00f4i d\u00f2ng v\u00e0 ng\u01b0\u1ee3c d\u00f2ng l\u00e0 $4$ gi\u1edd $10$ ph\u00fat$=\\dfrac {25}{6}$ gi\u1edd n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\dfrac {50}{x+5}+\\dfrac {50}{x-5}=\\dfrac {25}{6}$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":955},{"time":24,"part":[{"title":"Ch\u1ecdn <u>nh\u1eefng<\/u> bi\u1ec3u th\u1ee9c th\u00edch h\u1ee3p \u0111i\u1ec1n v\u00e0o d\u1ea5u ?","title_trans":"","temp":"checkbox","correct":[["2","3"]],"list":[{"point":10,"img":"","ques":"N\u0103m nay tu\u1ed5i anh g\u1ea5p $3$ l\u1ea7n tu\u1ed5i em. Sau $6$ n\u0103m n\u1eefa tu\u1ed5i anh ch\u1ec9 g\u1ea5p $2$ l\u1ea7n tu\u1ed5i em. H\u1ecfi n\u0103m nay em bao nhi\u00eau tu\u1ed5i?<br\/><table><tr><th><\/th><th>N\u0103m nay<\/th><th>$6$ n\u0103m n\u1eefa<\/th><\/tr><tr><td>Anh<\/td><td>$3x$<\/td><td>?<\/td><\/tr><tr><td>Em<\/td><td>$x$<\/td><td>$x+6$<\/td><\/tr><\/table>","hint":"","column":2,"number_true":2,"select":["A. $x.2$","B. $3x+6$","C. $(x+6).2$","D. $2x+6$"],"explain":"<span class='basic_left'>G\u1ecdi s\u1ed1 tu\u1ed5i n\u0103m nay c\u1ee7a em l\u00e0 $x$ (tu\u1ed5i, $x\\in \\mathbb N^*$) <br\/> V\u00ec n\u0103m nay, tu\u1ed5i anh g\u1ea5p $3$ l\u1ea7n tu\u1ed5i em n\u00ean tu\u1ed5i anh l\u00e0 $3x$ (tu\u1ed5i) <br\/> $6$ n\u0103m n\u1eefa tu\u1ed5i em l\u00e0 $x+6$ (tu\u1ed5i) <br\/> \u0110\u1ec3 x\u00e1c \u0111\u1ecbnh bi\u1ec3u th\u1ee9c trong \u00f4 tr\u1ed1ng ch\u00fang ta c\u00f3 hai c\u00e1ch sau: <br\/> <b> C\u00e1ch 1:<\/b> \u0110i t\u1eeb gi\u1ea3 thi\u1ebft $6$ n\u0103m n\u1eefa th\u00ec tu\u1ed5i anh l\u00e0 $3x+6$ (tu\u1ed5i) <br\/> <b>C\u00e1ch 2:<\/b> \u0110i t\u1eeb gi\u1ea3 thi\u1ebft $6$ n\u0103m n\u1eefa tu\u1ed5i anh g\u1ea5p $2$ l\u1ea7n tu\u1ed5i em th\u00ec tu\u1ed5i anh l\u00e0 $2(x+6)$ (tu\u1ed5i) <br\/> Khi \u0111\u00f3, ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $3x+6=2(x+6)$ <br\/> Do v\u1eady, bi\u1ec3u th\u1ee9c \u0111i\u1ec1n v\u00e0o d\u1ea5u ? l\u00e0 $3x+6$ ho\u1eb7c $2(x+6)$<br\/> <span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B v\u00e0 C.<\/span><\/span>"}]}],"id_ques":956},{"time":24,"part":[{"title":"Ch\u1ecdn <u>nh\u1eefng<\/u> bi\u1ec3u th\u1ee9c th\u00edch h\u1ee3p \u0111i\u1ec1n v\u00e0o d\u1ea5u ?","title_trans":"","temp":"checkbox","correct":[["1","3"]],"list":[{"point":10,"img":"","ques":"N\u0103m nay tu\u1ed5i b\u1ed1 h\u01a1n tu\u1ed5i con l\u00e0 $25$ tu\u1ed5i. Sau $5$ n\u0103m n\u1eefa tu\u1ed5i b\u1ed1 b\u1eb1ng $\\dfrac {8}{3}$ tu\u1ed5i con. H\u1ecfi n\u0103m nay con bao nhi\u00eau tu\u1ed5i?<br\/><table><tr><th><\/th><th>N\u0103m nay<\/th><th>$5$ n\u0103m n\u1eefa<\/th><\/tr><tr><td>B\u1ed1<\/td><td>$x+25$<\/td><td>?<\/td><\/tr><tr><td>Con<\/td><td>$x$<\/td><td>$x+5$<\/td><\/tr><\/table>","hint":"","column":2,"number_true":2,"select":["A. $x+30$","B. $5x$","C. $\\dfrac {8}{3}(x+5)$","D. $5x+5$"],"explain":"<span class='basic_left'>G\u1ecdi s\u1ed1 tu\u1ed5i n\u0103m nay c\u1ee7a con l\u00e0 $x$ (tu\u1ed5i, $x\\in \\mathbb N^*$)<br\/>V\u00ec n\u0103m nay, tu\u1ed5i b\u1ed1 h\u01a1n tu\u1ed5i con l\u00e0 $25$ tu\u1ed5i n\u00ean tu\u1ed5i b\u1ed1 l\u00e0 $25+x$ (tu\u1ed5i)<br\/>$5$ n\u0103m n\u1eefa tu\u1ed5i b\u1ed1 l\u00e0 $x+25+5=x+30$ (tu\u1ed5i)<br\/>$5$ n\u0103m n\u1eefa tu\u1ed5i con l\u00e0 $x+5$ (tu\u1ed5i)<br\/>V\u00ec $5$ n\u0103m n\u1eefa tu\u1ed5i b\u1ed1 b\u1eb1ng $\\dfrac {8}{3}$ tu\u1ed5i con n\u00ean tu\u1ed5i b\u1ed1 $5$ n\u0103m n\u1eefa l\u00e0 $\\dfrac {8}{3}(x+5)$ (tu\u1ed5i)<br\/>Khi \u0111\u00f3, ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: $x+30=\\dfrac {8}{3}(x+5)$<br\/>V\u1eady bi\u1ec3u th\u1ee9c c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $\\dfrac {8}{3}(x+5)$ ho\u1eb7c $x+30$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A v\u00e0 C.<\/span><\/span>"}]}],"id_ques":957},{"time":24,"part":[{"title":"\u0110i\u1ec1n bi\u1ec3u th\u1ee9c th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["x"],["30-x"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<span class='basic_left'>Tr\u00ean qu\u00e3ng \u0111\u01b0\u1eddng $AB$ d\u00e0i $30km$, m\u1ed9t ng\u01b0\u1eddi \u0111i t\u1eeb $A$ \u0111\u1ebfn $C$ ($C$ n\u1eb1m gi\u1eefa $A$ v\u00e0 $B$) v\u1edbi v\u1eadn t\u1ed1c $30 km\/h$, r\u1ed3i \u0111i t\u1eeb $C$ \u0111\u1ebfn $B$ v\u1edbi v\u1eadn t\u1ed1c $20km\/h$. Th\u1eddi gian \u0111i h\u1ebft qu\u00e3ng \u0111\u01b0\u1eddng $AB$ l\u00e0 $1$ gi\u1edd $10$ ph\u00fat. T\u00ednh qu\u00e3ng \u0111\u01b0\u1eddng $AC$ v\u00e0 $CB.$<br\/>G\u1ecdi qu\u00e3ng \u0111\u01b0\u1eddng $AC$ l\u00e0 $x$ ($km$). Ph\u01b0\u01a1ng tr\u00ecnh bi\u1ec3u th\u1ecb b\u00e0i to\u00e1n l\u00e0: $\\dfrac {\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{30}+\\dfrac {\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{20}=\\dfrac {7}{6}$<\/span>","hint":"T\u00ecm m\u1ed1i li\u00ean h\u1ec7 gi\u1eefa th\u1eddi gian \u0111i qu\u00e3ng \u0111\u01b0\u1eddng $AC$ v\u00e0 $CB$.","explain":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/D8_B21D1.2.png' \/><\/center><span class='basic_left'>G\u1ecdi qu\u00e3ng \u0111\u01b0\u1eddng $AC$ d\u00e0i $x$ ($km, \\,x>0$)<br\/>V\u00ec $C$ n\u1eb1m gi\u1eefa $A$ v\u00e0 $B$ n\u00ean qu\u00e3ng \u0111\u01b0\u1eddng $CB$ l\u00e0 $30-x$ ($km$)<br\/>V\u00ec ng\u01b0\u1eddi \u0111\u00f3 \u0111i t\u1eeb $A$ \u0111\u1ebfn $C$ v\u1edbi v\u1eadn t\u1ed1c $30 km\/h$ n\u00ean th\u1eddi gian \u0111i h\u1ebft qu\u00e3ng \u0111\u01b0\u1eddng $AC$ l\u00e0 $\\dfrac {x}{30}$ (gi\u1edd)<br\/>V\u00ec ng\u01b0\u1eddi \u0111\u00f3 \u0111i t\u1eeb $C$ \u0111\u1ebfn $B$ v\u1edbi v\u1eadn t\u1ed1c $20km\/h$ n\u00ean th\u1eddi gian \u0111i h\u1ebft qu\u00e3ng \u0111\u01b0\u1eddng $BC$ l\u00e0 $\\dfrac {30-x}{20}$ (gi\u1edd)<br\/>V\u00ec t\u1ed5ng th\u1eddi gian \u0111i h\u1ebft qu\u00e3ng \u0111\u01b0\u1eddng l\u00e0 $1$ gi\u1edd $10$ ph\u00fat $=\\dfrac {7}{6}$ gi\u1edd n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh:<br\/>$\\dfrac {x}{30}+\\dfrac {30-x}{20}=\\dfrac {7}{6}$<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $x$ v\u00e0 $30-x$<\/span> <\/span>"}]}],"id_ques":958},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["5"],["15"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"M\u1ed9t s\u1ed1 h\u1ecdc sinh nam v\u00e0 n\u1eef tham gia m\u1ed9t tr\u00f2 ch\u01a1i. L\u00fac \u0111\u1ea7u, s\u1ed1 h\u1ecdc sinh nam b\u1eb1ng $\\dfrac {1}{3}$ s\u1ed1 h\u1ecdc sinh n\u1eef. Sau \u0111\u00f3, c\u00f3 th\u00eam $5$ b\u1ea1n nam tham gia v\u00e0 $5$ b\u1ea1n n\u1eef chuy\u1ec3n sang tr\u00f2 ch\u01a1i kh\u00e1c n\u00ean s\u1ed1 b\u1ea1n nam b\u1eb1ng s\u1ed1 b\u1ea1n n\u1eef. T\u00ednh s\u1ed1 h\u1ecdc sinh nam v\u00e0 n\u1eef ban \u0111\u1ea7u.<br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_ (nam); _input_ (n\u1eef)","hint":"G\u1ecdi s\u1ed1 h\u1ecdc sinh nam l\u00e0 $x$.","explain":"<span class='basic_left'>G\u1ecdi s\u1ed1 h\u1ecdc sinh nam l\u00e0 $x$ (h\u1ecdc sinh, $x\\in\\mathbb N^*$)<br\/>V\u00ec l\u00fac \u0111\u1ea7u, s\u1ed1 h\u1ecdc sinh nam b\u1eb1ng $\\dfrac {1}{3}$ s\u1ed1 h\u1ecdc sinh n\u1eef n\u00ean s\u1ed1 h\u1ecdc sinh n\u1eef l\u00e0 $3x$ (b\u1ea1n n\u1eef)<br\/>V\u00ec c\u00f3 th\u00eam $5$ b\u1ea1n nam tham gia n\u00ean l\u00fac sau c\u00f3 $x+5$ b\u1ea1n nam.<br\/>V\u00ec $5$ b\u1ea1n n\u1eef chuy\u1ec3n sang tr\u00f2 ch\u01a1i kh\u00e1c n\u00ean l\u00fac sau c\u00f3 $3x-5$ b\u1ea1n n\u1eef<br\/>V\u00ec l\u00fac sau, s\u1ed1 b\u1ea1n nam b\u1eb1ng s\u1ed1 b\u1ea1n n\u1eef n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: <br\/>$x+5=3x-5\\\\ \\Leftrightarrow 2x=10\\\\ \\Leftrightarrow x=5\\,\\,\\,\\text {(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady c\u00f3 $5$ b\u1ea1n nam v\u00e0 $15$ b\u1ea1n n\u1eef<br\/><span class='basic_pink'>V\u1eady c\u00e1c s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $5$ v\u00e0 $15$<\/span> <\/span>"}]}],"id_ques":959},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["300"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"M\u1ed9t \u0111\u1ed9i c\u00f4ng nh\u00e2n s\u1eeda m\u1ed9t \u0111o\u1ea1n \u0111\u01b0\u1eddng. Trong ng\u00e0y \u0111\u1ea7u, \u0111\u1ed9i s\u1eeda \u0111\u01b0\u1ee3c $\\dfrac {1}{3}$ qu\u00e3ng \u0111\u01b0\u1eddng. Ng\u00e0y th\u1ee9 hai \u0111\u1ed9i s\u1eeda \u0111\u01b0\u1ee3c $\\dfrac {1}{2}$ qu\u00e3ng \u0111\u01b0\u1eddng. Ng\u00e0y th\u1ee9 ba \u0111\u1ed9i s\u1eeda n\u1ed1t $50m$ \u0111\u01b0\u1eddng c\u00f2n l\u1ea1i. H\u1ecfi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng t\u1ed5ng c\u1ed9ng \u0111\u1ed9i c\u00f4ng nh\u00e2n s\u1eeda \u0111\u01b0\u1ee3c l\u00e0 bao nhi\u00eau?<br\/><b>\u0110\u00e1p s\u1ed1: <\/b> _input_ ($m$)","hint":"G\u1ecdi \u0111\u1ed9 d\u00e0i \u0111o\u1ea1n \u0111\u01b0\u1eddng l\u00e0 $x$ ($m$)","explain":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/daiso/bai21/lv1/img\/D8_B21D1.3.png' \/><\/center><span class='basic_left'>G\u1ecdi \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng \u0111\u1ed9i c\u00f4ng nh\u00e2n ph\u1ea3i s\u1eeda l\u00e0 $x$ ($m,\\, x>0$)<br\/>V\u00ec ng\u00e0y \u0111\u1ea7u, \u0111\u1ed9i s\u1eeda \u0111\u01b0\u1ee3c $\\dfrac {1}{3}$ qu\u00e3ng \u0111\u01b0\u1eddng l\u00e0 $\\dfrac {1}{3}x$ ($m$)<br\/>V\u00ec ng\u00e0y th\u1ee9 hai \u0111\u1ed9i s\u1eeda \u0111\u01b0\u1ee3c $\\dfrac {1}{2}$ qu\u00e3ng \u0111\u01b0\u1eddng l\u00e0 $\\dfrac {1}{2}x$ ($m$)<br\/>\u0110\u1ed9 d\u00e0i \u0111o\u1ea1n \u0111\u01b0\u1eddng c\u00f2n l\u1ea1i sau hai ng\u00e0y s\u1eeda l\u00e0 $50$ $m$ n\u00ean ta c\u00f3 ph\u01b0\u01a1ng tr\u00ecnh: <br\/>$x-\\dfrac {1}{3}x-\\dfrac {1}{2}x=50\\\\ \\Leftrightarrow \\dfrac {1}{6}x=50 \\\\ \\Leftrightarrow x=300 \\,\\,\\,\\text {(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady \u0111\u1ed9 d\u00e0i qu\u00e3ng \u0111\u01b0\u1eddng t\u1ed5ng c\u1ed9ng \u0111\u1ed9i c\u00f4ng nh\u00e2n \u0111\u00e3 s\u1eeda l\u00e0 $300 \\, m$<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng l\u00e0 $300$<\/span> <\/span>"}]}],"id_ques":960}],"lesson":{"save":0,"level":1}}