{"segment":[{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<span class='basic_left'>Kh\u1ed1i l\u01b0\u1ee3ng c\u1ee7a $40$ con l\u1ee3n \u0111\u01b0\u1ee3c ch\u1ecdn ng\u1eabu nhi\u00ean trong l\u00f4 th\u1eed nghi\u1ec7m (theo ph\u01b0\u01a1ng ph\u00e1p khoa h\u1ecdc) v\u00e0 l\u00f4 \u0111\u1ed1i ch\u1ee9ng (theo ph\u01b0\u01a1ng ph\u00e1p c\u0169) \u0111\u01b0\u1ee3c l\u00e0m tr\u00f2n \u0111\u1ebfn kg nh\u01b0 sau: <br\/> L\u00f4 th\u1eed nghi\u1ec7m <br\/> <table><tr><th>Gi\u00e1 tr\u1ecb $(x)$<\/th><th>121<\/th><th>128<\/th><th>130<\/th><th>135<\/th><th>138<\/th><th>140<\/th><th><\/th><\/tr><tr><td>T\u1ea7n s\u1ed1 $(n)$<\/td><td>2<\/td><td>3<\/td><td>6<\/td><td>4<\/td><td>3<\/td><td>2<\/td><td>$N=20$<\/td><\/tr><\/table> <br\/> L\u00f4 \u0111\u1ed1i ch\u1ee9ng <br\/> <table><tr><th>Gi\u00e1 tr\u1ecb $(x)$<\/th><th>120<\/th><th>123<\/th><th>128<\/th><th>130<\/th><th>133<\/th><th>135<\/th><th>140<\/th><th><\/th><\/tr><tr><td>T\u1ea7n s\u1ed1 $(n)$<\/td><td>2<\/td><td>3<\/td><td>4<\/td><td>5<\/td><td>3<\/td><td>2<\/td><td>1<\/td><td>$N=20$<\/td><\/tr><\/table> <br\/> Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t \u0111\u1ec3 \u0111i\u1ec1n v\u00e0o ch\u1ed7 tr\u1ed1ng trong kh\u1eb3ng \u0111\u1ecbnh sau: <br\/> Tr\u1ecdng l\u01b0\u1ee3ng trung b\u00ecnh m\u1ed7i con l\u1ee3n \u1edf l\u00f4 th\u1eed nghi\u1ec7m so v\u1edbi l\u00f4 \u0111\u1ed1i ch\u1ee9ng _____ <\/span>","select":["A. T\u0103ng $3\\, kg$","B. Gi\u1ea3m $3\\, kg$","C. T\u0103ng $2\\, kg$ ","D. Gi\u1ea3m $2\\,kg$"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>T\u00ednh s\u1ed1 trung b\u00ecnh c\u1ed9ng tr\u1ecdng l\u01b0\u1ee3ng c\u1ee7a m\u1ed7i con l\u1ee3n \u1edf t\u1eebng l\u00f4, sau \u0111\u00f3 so s\u00e1nh. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>L\u00f4 th\u1eed nghi\u1ec7m<br\/><table><tr><th>Gi\u00e1 tr\u1ecb $(x)$<\/th><th>121<\/th><th>128<\/th><th>130<\/th><th>135<\/th><th>138<\/th><th>140<\/th><th><\/th><\/tr><tr><td>T\u1ea7n s\u1ed1 $(n)$<\/td><td>2<\/td><td>3<\/td><td>6<\/td><td>4<\/td><td>3<\/td><td>2<\/td><td>$N=20$<\/td><\/tr><tr><td>C\u00e1c t\u00edch $(x.n)$<\/td><td>242<\/td><td>384<\/td><td>780<\/td><td>540<\/td><td>414<\/td><td>280<\/td><td>T\u1ed5ng: 2640<\/td><\/tr><\/table> <br\/> $\\Rightarrow \\overline{{{X}_{1}}}=\\dfrac{2640}{20}=132$ (kg) (1) <br\/> L\u00f4 \u0111\u1ed1i ch\u1ee9ng <table><tr><th>Gi\u00e1 tr\u1ecb $(x)$<\/th><th>120<\/th><th>123<\/th><th>128<\/th><th>130<\/th><th>133<\/th><th>135<\/th><th>140<\/th><th><\/th><\/tr><tr><td>T\u1ea7n s\u1ed1 $(n)$<\/td><td>2<\/td><td>3<\/td><td>4<\/td><td>5<\/td><td>3<\/td><td>2<\/td><td>1<\/td><td>$N=20$<\/td><\/tr><tr><td>C\u00e1c t\u00edch $(x.n)$<\/td><td>240<\/td><td>369<\/td><td>512<\/td><td>650<\/td><td>399<\/td><td>270<\/td><td>140<\/td><td>T\u1ed5ng: $2580$<\/td><\/tr><\/table> <br\/> $\\Rightarrow \\overline{{{X}_{2}}}=\\dfrac{2580}{20}=129$ (kg) (2) <br\/> T\u1eeb (1) v\u00e0 (2) ta th\u1ea5y tr\u1ecdng l\u01b0\u1ee3ng trung b\u00ecnh m\u1ed7i con l\u1ee3n \u1edf l\u00f4 th\u1eed nghi\u1ec7m so v\u1edbi l\u00f4 \u0111\u1ed1i ch\u1ee9ng t\u0103ng $3\\,kg.$ <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 A.<\/span> <\/span>","column":2}]}],"id_ques":981},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 \u0111\u00fang nh\u1ea5t v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["14,5","14.5"]]],"list":[{"point":10,"width":40,"content":"","type_input":"","ques":" <span class='basic_left'> Trung b\u00ecnh c\u1ed9ng c\u1ee7a $24$ s\u1ed1 l\u00e0 $15.$ N\u1ebfu lo\u1ea1i \u0111i hai s\u1ed1 $20$ v\u00e0 $21$ th\u00ec trung b\u00ecnh c\u1ed9ng c\u1ee7a c\u00e1c s\u1ed1 c\u00f2n l\u1ea1i b\u1eb1ng bao nhi\u00eau? <br\/> <b> \u0110\u00e1p \u00e1n: <\/b> _input_ <\/span>","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>T\u00ednh t\u1ed5ng c\u1ee7a $22$ s\u1ed1 c\u00f2n l\u1ea1i (sau khi b\u1ecf hai s\u1ed1 $20$ v\u00e0 $21$) <br\/> T\u00ednh s\u1ed1 trung b\u00ecnh c\u1ee7a $22$ s\u1ed1 c\u00f2n l\u1ea1i \u0111\u00f3. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Trung b\u00ecnh c\u1ed9ng c\u1ee7a $24$ s\u1ed1 l\u00e0 $15$ th\u00ec t\u1ed5ng c\u1ee7a $24$ s\u1ed1 l\u00e0: $24.15=360$ <br\/> T\u1ed5ng c\u1ee7a $22$ s\u1ed1 (sau khi lo\u1ea1i hai s\u1ed1 $20$ v\u00e0 $21$) l\u00e0: <br\/> $360-20-21=319$ <br\/> S\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a $22$ s\u1ed1 c\u00f2n l\u1ea1i l\u00e0: <br\/> $\\dfrac{319}{22}=14,5$ <br\/> <span class='basic_pink'> V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $14,5$<\/span><\/span>"}]}],"id_ques":982},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<span class='basic_left'>H\u1ecdc sinh l\u1edbp $7A$ tr\u01b0\u1eddng Trung h\u1ecdc c\u01a1 s\u1edf Nguy\u1ec5n Tr\u00e3i \u0111\u01b0\u1ee3c ph\u00e2n lo\u1ea1i v\u1ec1 h\u1ecdc l\u1ef1c nh\u01b0 sau: $20\\%$ lo\u1ea1i gi\u1ecfi, $25\\%$ lo\u1ea1i kh\u00e1, $50\\%$ lo\u1ea1i trung b\u00ecnh, $5\\%$ lo\u1ea1i y\u1ebfu. <br\/> Ta c\u00f3 bi\u1ec3u \u0111\u1ed3 h\u00ecnh qu\u1ea1t bi\u1ec3u di\u1ec5n s\u1ef1 ph\u00e2n lo\u1ea1i theo d\u1eef ki\u1ec7n tr\u00ean l\u00e0: <center><img src='https://www.luyenthi123.com/file/luyenthi123/lop7/toan/daiso/bai22/lv3/img\/D7B22K1_7.png' \/><\/center> <\/span>","select":["\u0110\u00fang","Sai"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Ta ki\u1ec3m tra c\u00e1c v\u1ea5n \u0111\u1ec1 sau: <br\/> - C\u00e1c v\u00f9ng \u0111\u00e1nh d\u1ea5u s\u1ed1 ph\u1ea7n tr\u0103m x\u1ebfp lo\u1ea1i h\u1ecdc l\u1ef1c c\u1ee7a h\u1ecdc sinh trong bi\u1ec3u \u0111\u1ed3 c\u00f3 \u0111\u00fang kh\u00f4ng. <br\/> - S\u1ed1 \u0111o g\u00f3c \u1edf t\u00e2m c\u00f3 t\u01b0\u01a1ng \u1ee9ng v\u1edbi s\u1ed1 ph\u1ea7n tr\u0103m x\u1ebfp lo\u1ea1i h\u1ecdc l\u1ef1c kh\u00f4ng. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>T\u1eeb s\u1ed1 li\u1ec7u \u0111\u00e3 cho, ta c\u00f3 th\u1ec3 bi\u1ec3u di\u1ec5n b\u1eb1ng bi\u1ec3u \u0111\u1ed3 h\u00ecnh qu\u1ea1t nh\u01b0 sau: <br\/> - D\u1ef1ng h\u00ecnh tr\u00f2n c\u00f3 b\u00e1n k\u00ednh t\u1ef1 ch\u1ecdn <br\/> - H\u00ecnh tr\u00f2n n\u00e0y \u0111\u01b0\u1ee3c chia th\u00e0nh c\u00e1c h\u00ecnh qu\u1ea1t m\u00e0 g\u00f3c \u1edf t\u00e2m c\u1ee7a h\u00ecnh qu\u1ea1t t\u1ec9 l\u1ec7 v\u1edbi t\u1ea7n su\u1ea5t (ph\u1ea7n tr\u0103m lo\u1ea1i h\u1ecdc sinh) <br\/> $20\\%$ lo\u1ea1i gi\u1ecfi th\u00ec g\u00f3c \u1edf t\u00e2m l\u00e0: $20\\%{{.360}^{o}}=\\dfrac{20}{100}{{.360}^{o}}={{72}^{o}}$ <br\/> T\u01b0\u01a1ng t\u1ef1, $25\\%$ lo\u1ea1i kh\u00e1 th\u00ec g\u00f3c \u1edf t\u00e2m l\u00e0: $90^o$ <br\/> $50\\%$ lo\u1ea1i trung b\u00ecnh th\u00ec g\u00f3c \u1edf t\u00e2m l\u00e0: $180^o$ <br\/> $5\\%$ lo\u1ea1i y\u1ebfu th\u00ec g\u00f3c \u1edf t\u00e2m l\u00e0: $18^o$ <br\/> Do \u0111\u00f3, bi\u1ec3u \u0111\u1ed3 h\u00ecnh qu\u1ea1t trong \u0111\u1ec1 b\u00e0i ho\u00e0n to\u00e0n \u0111\u00fang v\u1edbi s\u1ed1 li\u1ec7u \u0111\u00e3 cho. <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span> <br\/> <b> L\u01b0u \u00fd: <\/b> <i> \u0110\u1ed1i v\u1edbi c\u00e1c b\u00e0i v\u1ebd bi\u1ec3u \u0111\u1ed3 h\u00ecnh qu\u1ea1t v\u1edbi c\u00e1c s\u1ed1 li\u1ec7u \u0111\u00e3 cho tr\u01b0\u1edbc, ta l\u00e0m nh\u01b0 sau: <br\/> + D\u1ef1ng h\u00ecnh tr\u00f2n c\u00f3 b\u00e1n k\u00ednh t\u1ef1 ch\u1ecdn <br\/> + X\u00e1c \u0111\u1ecbnh s\u1ed1 ph\u1ea7n tr\u0103m c\u1ee7a t\u1eebng \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u01b0\u1ee3c x\u00e9t <br\/> + T\u00ednh s\u1ed1 \u0111o g\u00f3c \u1edf t\u00e2m theo t\u1eebng s\u1ed1 ph\u1ea7n tr\u0103m c\u1ee7a t\u1eebng \u0111\u1ed1i t\u01b0\u1ee3ng \u0111\u00f3. <br\/> C\u00f4ng th\u1ee9c t\u00ednh g\u00f3c \u1edf t\u00e2m nh\u01b0 sau: (S\u1ed1 ph\u1ea7n tr\u0103m) $\\times 360^o$ <\/i> <\/span>","column":2}]}],"id_ques":983},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<span class='basic_left'>M\u1ed9t b\u1ea3ng s\u1ed1 li\u1ec7u \u0111i\u1ec1u tra c\u00f3 $20$ gi\u00e1 tr\u1ecb. N\u1ebfu m\u1ed7i gi\u00e1 tr\u1ecb c\u1ee7a d\u1ea5u hi\u1ec7u t\u0103ng th\u00eam $2$ \u0111\u01a1n v\u1ecb th\u00ec s\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a d\u1ea5u hi\u1ec7u \u0111\u00f3 t\u0103ng th\u00eam bao nhi\u00eau \u0111\u01a1n v\u1ecb?<\/span>","select":["A. $20$","B. $2$","C. $10$","D. $4$"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Vi\u1ebft c\u00f4ng th\u1ee9c t\u00ednh s\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a $20$ gi\u00e1 tr\u1ecb d\u1ea1ng t\u1ed5ng qu\u00e1t. <br\/> Sau \u0111\u00f3 th\u00eam m\u1ed7i gi\u00e1 tr\u1ecb $2$ \u0111\u01a1n v\u1ecb v\u00e0 t\u00ednh s\u1ed1 trung b\u00ecnh m\u1edbi. <br\/> So s\u00e1nh s\u1ed1 trung b\u00ecnh c\u0169 v\u00e0 s\u1ed1 trung b\u00ecnh m\u1edbi <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> Ta c\u00f3: <br\/> ${{\\overline{X}}_{\\text{\u0111}}}=\\dfrac{{{x}_{1}}{{n}_{1}}+{{x}_{2}}{{n}_{2}}+\\cdots +{{x}_{20}}{{n}_{20}}}{N}$ v\u1edbi $N={{n}_{1}}+{{n}_{2}}+\\cdots +{{n}_{20}}$ <br\/> M\u1ed7i gi\u00e1 tr\u1ecb c\u1ee7a d\u1ea5u hi\u1ec7u t\u0103ng th\u00eam $2$ \u0111\u01a1n v\u1ecb th\u00ec: <br\/> $\\begin{align} & {{\\overline{X}}_{s}}=\\dfrac{\\left( {{x}_{1}}+2 \\right){{n}_{1}}+\\left( {{x}_{2}}+2 \\right){{n}_{2}}+\\cdots +\\left( {{x}_{20}}+2 \\right){{n}_{20}}}{N} \\\\ & \\,\\,\\,\\,\\,\\,\\,=\\dfrac{{{x}_{1}}{{n}_{1}}+2{{n}_{1}}+{{x}_{2}}{{n}_{2}}+2{{n}_{2}}+\\cdots +{{x}_{20}}{{n}_{20}}+2{{n}_{20}}}{N} \\\\ & \\,\\,\\,\\,\\,\\,\\,=\\dfrac{\\left( {{x}_{1}}{{n}_{1}}+{{x}_{2}}{{n}_{2}}+\\cdots +{{x}_{20}}{{n}_{20}} \\right)+\\left( 2{{n}_{1}}+2{{n}_{2}}+\\cdots +2{{n}_{20}} \\right)}{N} \\\\ & \\,\\,\\,\\,\\,\\,\\,=\\dfrac{{{x}_{1}}{{n}_{1}}+{{x}_{2}}{{n}_{2}}+\\cdots +{{x}_{20}}{{n}_{20}}}{N}+\\dfrac{2{{n}_{1}}+2{{n}_{2}}+\\cdots +2{{n}_{20}}}{N} \\\\ & \\,\\,\\,\\,\\,\\,=\\overline{{{X}_{\\text{\u0111}}}}+\\dfrac{2\\left( {{n}_{1}}+{{n}_{2}}+\\cdots {{n}_{20}} \\right)}{N} \\\\ & \\,\\,\\,\\,\\,\\,=\\overline{{{X}_{\\text{\u0111}}}}+\\dfrac{2N}{N} \\\\ & \\,\\,\\,\\,\\,=\\overline{{{X}_{\\text{\u0111}}}}+2 \\\\ \\end{align}$ <br\/> $\\Rightarrow$ S\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac sau t\u0103ng $2$ \u0111\u01a1n v\u1ecb so v\u1edbi s\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac \u0111\u1ea7u. <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B.<\/span><\/span>","column":4}]}],"id_ques":984},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[1]],"list":[{"point":10,"ques":"<span class='basic_left'>Kh\u1eb3ng \u0111\u1ecbnh sau \u0111\u00e2y \u0110\u00fang hay Sai? <br\/> N\u1ebfu nh\u00e2n m\u1ed7i gi\u00e1 tr\u1ecb c\u1ee7a d\u1ea5u hi\u1ec7u v\u1edbi m\u1ed9t h\u1eb1ng s\u1ed1 th\u00ec s\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a d\u1ea5u hi\u1ec7u c\u0169ng nh\u00e2n l\u00ean v\u1edbi h\u1eb1ng s\u1ed1 \u0111\u00f3.<\/span>","select":["\u0110\u00fang","Sai"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>Vi\u1ebft c\u00f4ng th\u1ee9c t\u00ednh s\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a d\u1ea5u hi\u1ec7u d\u1ea1ng t\u1ed5ng qu\u00e1t. <br\/> Sau \u0111\u00f3 nh\u00e2n m\u1ed7i gi\u00e1 tr\u1ecb v\u1edbi h\u1eb1ng s\u1ed1 $a$ v\u00e0 t\u00ednh s\u1ed1 trung b\u00ecnh m\u1edbi. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>Ta c\u00f3: <br\/> ${{\\overline{X}}_{\\text{\u0111}}}=\\dfrac{{{x}_{1}}{{n}_{1}}+{{x}_{2}}{{n}_{2}}+\\cdots +{{x}_{k}}{{n}_{k}}}{N}$ v\u1edbi $N={{n}_{1}}+{{n}_{2}}+\\cdots +{{n}_{k}}$ <br\/> M\u1ed7i gi\u00e1 tr\u1ecb c\u1ee7a d\u1ea5u hi\u1ec7u nh\u00e2n v\u1edbi h\u1eb1ng s\u1ed1 $a$, ta \u0111\u01b0\u1ee3c: <br\/> $\\begin{align} & {{\\overline{X}}_{s}}=\\dfrac{a{{x}_{1}}{{n}_{1}}+a{{x}_{2}}{{n}_{2}}+\\cdots +a{{x}_{k}}{{n}_{k}}}{N} \\\\ & \\,\\,\\,\\,\\,\\,\\,\\,=\\dfrac{a\\left( {{x}_{1}}{{n}_{1}}+{{x}_{2}}{{n}_{2}}+\\cdots +{{x}_{k}}{{n}_{k}} \\right)}{N} \\\\ & \\,\\,\\,\\,\\,\\,\\,=a\\overline{{{X}_{\\text{\u0111}}}} \\\\ \\end{align}$ <br\/> $\\Rightarrow$ N\u1ebfu nh\u00e2n m\u1ed7i gi\u00e1 tr\u1ecb c\u1ee7a d\u1ea5u hi\u1ec7u v\u1edbi m\u1ed9t h\u1eb1ng s\u1ed1 th\u00ec s\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a d\u1ea5u hi\u1ec7u c\u0169ng nh\u00e2n l\u00ean v\u1edbi h\u1eb1ng s\u1ed1 \u0111\u00f3. <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 \u0110\u00fang.<\/span><\/span>","column":2}]}],"id_ques":985},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[4]],"list":[{"point":10,"ques":"<span class='basic_left'>M\u1ed9t tr\u01b0\u1eddng THCS c\u00f3 $40$ th\u1ea7y c\u00f4 gi\u00e1o, tu\u1ed5i trung b\u00ecnh l\u00e0 $42,1.$ Sang n\u0103m h\u1ecdc m\u1edbi, c\u00f3 m\u1ed9t th\u1ea7y gi\u00e1o $60$ tu\u1ed5i v\u00e0 m\u1ed9t c\u00f4 gi\u00e1o $55$ tu\u1ed5i ngh\u1ec9 h\u01b0u. Nh\u00e0 tr\u01b0\u1eddng nh\u1eadn th\u00eam m\u1ed9t c\u00f4 gi\u00e1o $21$ tu\u1ed5i v\u00e0 m\u1ed9t th\u1ea7y gi\u00e1o $22$ tu\u1ed5i. Tu\u1ed5i trung b\u00ecnh c\u1ee7a c\u00e1c th\u1ea7y c\u00f4 gi\u00e1o c\u1ee7a tr\u01b0\u1eddng trong n\u0103m h\u1ecdc m\u1edbi l\u00e0: <\/span>","select":["A. $25$ tu\u1ed5i","B. $30$ tu\u1ed5i","C. $35,5$ tu\u1ed5i","D. $40,3$ tu\u1ed5i"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>T\u00ednh t\u1ed5ng tu\u1ed5i c\u1ee7a $40$ th\u1ea7y c\u00f4 gi\u00e1o l\u00fac \u0111\u1ea7u. <br\/> T\u00ednh t\u1ed5ng tu\u1ed5i c\u1ee7a c\u00e1c th\u1ea7y c\u00f4 gi\u00e1o sau khi c\u00f3 s\u1ef1 thay \u0111\u1ed5i khi sang n\u0103m h\u1ecdc m\u1edbi. <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/> T\u1ed5ng tu\u1ed5i c\u1ee7a 40 th\u1ea7y c\u00f4 gi\u00e1o c\u1ee7a tr\u01b0\u1eddng l\u00fac \u0111\u1ea7u l\u00e0: <br\/> $42,1.40=1684$ (tu\u1ed5i) <br\/> Sang n\u0103m h\u1ecdc m\u1edbi, t\u1ed5ng tu\u1ed5i c\u1ee7a c\u00e1c th\u1ea7y c\u00f4 c\u1ee7a tr\u01b0\u1eddng (sau khi c\u00f3 s\u1ef1 lu\u00e2n chuy\u1ec3n) l\u00e0: <br\/> $1684-60-55+21+22=1612$ (tu\u1ed5i) <br\/> Tu\u1ed5i trung b\u00ecnh c\u1ee7a c\u00e1c th\u1ea7y c\u1ed1 gi\u00e1o c\u1ee7a tr\u01b0\u1eddng trong n\u0103m h\u1ecdc m\u1edbi l\u00e0: <br\/> $\\dfrac{1612}{40}=40,3$ (tu\u1ed5i) <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 D.<\/span><\/span>","column":4}]}],"id_ques":986},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 \u0111\u00fang nh\u1ea5t v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["56"]]],"list":[{"point":10,"width":40,"content":"","type_input":"","ques":" <span class='basic_left'> T\u00e1m \u0111\u1ed9i b\u00f3ng tham gia m\u1ed9t gi\u1ea3i b\u00f3ng \u0111\u00e1. M\u1ed7i \u0111\u1ed9i \u0111\u1ec1u ph\u1ea3i \u0111\u00e1 v\u1edbi m\u1ed7i \u0111\u1ed9i kh\u00e1c m\u1ed9t tr\u1eadn l\u01b0\u1ee3t \u0111i, m\u1ed9t tr\u1eadn l\u01b0\u1ee3t v\u1ec1. <br\/> <b>C\u00e2u 1. <\/b> To\u00e0n gi\u1ea3i c\u00f3 s\u1ed1 tr\u1eadn \u0111\u1ea5u l\u00e0 _input_ <\/span>","explain":"<span class='basic_left'>N\u1ebfu g\u1ecdi c\u00e1c \u0111\u1ed9i l\u1ea7n l\u01b0\u1ee3t l\u00e0 \u0111\u1ed9i $1,$..., \u0111\u1ed9i $8.$ <br\/> M\u1ed9t \u0111\u1ed9i \u0111\u00e1 v\u1edbi $7$ \u0111\u1ed9i c\u00f2n l\u1ea1i l\u00e0 $7$ tr\u1eadn. <br\/> V\u00ec c\u00f3 t\u1ea5t c\u1ea3 $8$ \u0111\u1ed9i n\u00ean c\u1ea3 gi\u1ea3i \u0111\u1ea5u c\u00f3: $7.8 = 56$ (tr\u1eadn) <br\/> (Trong \u0111\u00f3 m\u1ed7i \u0111\u1ed9i \u0111\u00e3 \u0111\u00e1 v\u1edbi m\u1ed9t \u0111\u1ed9i kh\u00e1c hai tr\u1eadn l\u00e0 tr\u1eadn l\u01b0\u1ee3t \u0111i v\u00e0 tr\u1eadn l\u01b0\u1ee3t v\u1ec1)<br\/> <span class='basic_pink'> V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $56.$<\/span> <br\/> <b> C\u00e1ch kh\u00e1c: <\/b> <br\/> <i> \u0110\u1ed9i th\u1ee9 nh\u1ea5t ph\u1ea3i \u0111\u00e1 v\u1edbi $7$ \u0111\u1ed9i c\u00f2n l\u1ea1i (c\u1ea3 l\u01b0\u1ee3t \u0111i v\u00e0 l\u01b0\u1ee3t v\u1ec1) n\u00ean c\u00f3 $14$ tr\u1eadn. <br\/> V\u00ec s\u1ed1 tr\u1eadn c\u1ee7a \u0111\u1ed9i th\u1ee9 hai \u0111\u00e1 v\u1edbi \u0111\u1ed9i th\u1ee9 nh\u1ea5t l\u00e0 $2$ tr\u1eadn, \u0111\u00e3 \u0111\u01b0\u1ee3c t\u00ednh n\u00ean \u0111\u1ed9i n\u00e0y ch\u1ec9 c\u00f2n \u0111\u00e1 $12$ tr\u1eadn. <br\/> \u0110\u1ed9i th\u1ee9 $3$ \u0111\u00e3 \u0111\u00e1 v\u1edbi \u0111\u1ed9i th\u1ee9 nh\u1ea5t v\u00e0 th\u1ee9 hai n\u00ean ch\u1ec9 c\u00f2n \u0111\u00e1 $10$ tr\u1eadn. <br\/> Ti\u1ebfp t\u1ee5c qu\u00e1 tr\u00ecnh l\u1eadp lu\u1eadn \u0111\u00f3 ta c\u00f3 s\u1ed1 tr\u1eadn c\u1ee7a c\u00e1c \u0111\u1ed9i th\u1ee9 t\u01b0, th\u1ee9 n\u0103m\u2026.., th\u1ee9 t\u00e1m ch\u1ec9 c\u00f2n l\u00e0: $8$ tr\u1eadn, $6$ tr\u1eadn, \u2026., $0$ tr\u1eadn <br\/> To\u00e0n gi\u1ea3i c\u00f3 s\u1ed1 tr\u1eadn \u0111\u1ea5u l\u00e0: <br\/> $14+12+10+8+6+4+2+0=56$(tr\u1eadn)<\/i> <\/span>"}]}],"id_ques":987},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<span class='basic_left'>T\u00e1m \u0111\u1ed9i b\u00f3ng tham gia m\u1ed9t gi\u1ea3i b\u00f3ng \u0111\u00e1. M\u1ed7i \u0111\u1ed9i \u0111\u1ec1u ph\u1ea3i \u0111\u00e1 v\u1edbi m\u1ed7i \u0111\u1ed9i kh\u00e1c m\u1ed9t tr\u1eadn l\u01b0\u1ee3t \u0111i, m\u1ed9t tr\u1eadn l\u01b0\u1ee3t v\u1ec1. <br\/> <b>C\u00e2u 2. <\/b> Ta c\u00f3 b\u1ea3ng v\u1ec1 s\u1ed1 b\u00e0n th\u1eafng trong m\u1ed7i tr\u1eadn v\u00e0 t\u1ea7n s\u1ed1 c\u1ee7a n\u00f3 nh\u01b0 sau: <br\/> <table><tr><th>S\u1ed1 b\u00e0n th\u1eafng m\u1ed7i tr\u1eadn $(x)$<\/th><th>1<\/th><th>2<\/th><th>3<\/th><th>4<\/th><th>5<\/th><th>6<\/th><\/tr><tr><td>S\u1ed1 tr\u1eadn (t\u1ea7n s\u1ed1)<\/td><td>5<\/td><td>14<\/td><td>17<\/td><td>10<\/td><td>3<\/td><td>2<\/td><\/tr><\/table> <br\/> S\u1ed1 b\u00e0n th\u1eafng trung b\u00ecnh c\u1ee7a m\u1ed7i tr\u1eadn l\u00e0: <\/span>","select":["A. $2$ b\u00e0n","B. $\\approx 2,7$ b\u00e0n","C. $3$ b\u00e0n","D. $\\approx 3,5$ b\u00e0n"],"explain":"<span class='basic_left'> Theo c\u00e2u 1, ta \u0111\u00e3 bi\u1ebft s\u1ed1 tr\u1eadn \u0111\u1ea5u c\u1ee7a c\u1ea3 gi\u1ea3i \u0111\u1ea5u l\u00e0: $56$ (tr\u1eadn). <br\/> S\u1ed1 b\u00e0n th\u1eafng trung b\u00ecnh c\u1ee7a m\u1ed7i tr\u1eadn l\u00e0: <br\/> $\\dfrac{1.5+2.14+3.17+4.10+5.3+6.2}{56}=\\dfrac{151}{56}\\approx 2,7$ (b\u00e0n) <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B.<\/span><\/span>","column":2}]}],"id_ques":988},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":10,"ques":"<span class='basic_left'>M\u1ed9t h\u1ecdc sinh vi\u1ebft $27$ s\u1ed1 r\u1ed3i t\u00ednh trung b\u00ecnh c\u1ee7a ch\u00fang, nh\u01b0ng sau \u0111\u00f3 l\u1ea1i vi\u1ebft ti\u1ebfp s\u1ed1 trung b\u00ecnh c\u1ed9ng \u0111\u00f3 b\u00ean c\u1ea1nh r\u1ed3i t\u00ednh lu\u00f4n s\u1ed1 trung b\u00ecnh c\u1ed9ng c\u1ee7a $28$ s\u1ed1. S\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac sau l\u1edbn h\u01a1n, nh\u1ecf h\u01a1n hay b\u1eb1ng s\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac \u0111\u1ea7u (trung b\u00ecnh c\u1ed9ng c\u1ee7a $27$ s\u1ed1).<\/span>","select":["A. L\u1edbn h\u01a1n","B. Nh\u1ecf h\u01a1n","C. B\u1eb1ng"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>G\u1ecdi trung b\u00ecnh c\u1ed9ng c\u1ee7a $27$ s\u1ed1 l\u00fac \u0111\u1ea7u l\u00e0 $a$ <br\/> T\u00ecm t\u1ed5ng c\u1ee7a $27$ s\u1ed1 l\u00fac \u0111\u1ea7u theo $a$ <br\/> T\u00ednh trung b\u00ecnh c\u1ed9ng l\u00fac sau theo $a.$ <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>G\u1ecdi s\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac \u0111\u1ea7u (trung b\u00ecnh c\u1ed9ng c\u1ee7a $27$ s\u1ed1) l\u00e0 $a.$ <br\/> T\u1ed5ng c\u1ee7a $27$ s\u1ed1 l\u00e0: $27a$ <br\/> S\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac sau l\u00e0: $\\dfrac{27a+a}{28}=\\dfrac{28a}{28}=a$ <br\/> $\\Rightarrow$ S\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac sau b\u1eb1ng s\u1ed1 trung b\u00ecnh c\u1ed9ng l\u00fac \u0111\u1ea7u. <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 C.<\/span><\/span>","column":3}]}],"id_ques":989},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":10,"ques":"<span class='basic_left'>\u0110\u1ec3 t\u00ednh trung b\u00ecnh c\u1ed9ng c\u1ee7a ba s\u1ed1 $a,b,c$ b\u1ea1n T\u00e2m \u0111\u00e3 l\u1ea5y trung b\u00ecnh c\u1ed9ng c\u1ee7a $a$ v\u00e0 $b$, r\u1ed3i t\u00ednh trung b\u00ecnh c\u1ed9ng c\u1ee7a k\u1ebft qu\u1ea3 n\u00e0y v\u00e0 $c.$ Cho bi\u1ebft $a > b > c.$ C\u00e1ch t\u00ednh c\u1ee7a T\u00e2m cho k\u1ebft qu\u1ea3 l\u1edbn h\u01a1n, nh\u1ecf h\u01a1n hay b\u1eb1ng v\u1edbi k\u1ebft qu\u1ea3 \u0111\u00fang.<\/span>","select":["A. L\u1edbn h\u01a1n","B. Nh\u1ecf h\u01a1n","C. B\u1eb1ng"],"explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn:<\/span><br\/>T\u00ecm hi\u1ec7u k\u1ebft qu\u1ea3 gi\u1eefa hai s\u1ed1 trung b\u00ecnh c\u1ed9ng m\u00e0 T\u00e2m t\u00ednh v\u00e0 k\u1ebft qu\u1ea3 \u0111\u00fang. <br\/> So s\u00e1nh hi\u1ec7u \u0111\u00f3 v\u1edbi $0.$ <br\/> <span class='basic_green'>B\u00e0i gi\u1ea3i:<\/span><br\/>K\u1ebft qu\u1ea3 t\u00ednh s\u1ed1 trung b\u00ecnh c\u1ee7a ba s\u1ed1 $a, b, c$ \u0111\u00fang l\u00e0: $A=\\dfrac{a+b+c}{3}$ <br\/> K\u1ebft qu\u1ea3 m\u00e0 T\u00e2m t\u00ednh l\u00e0: $B=\\dfrac{\\dfrac{a+b}{2}+c}{2}=\\dfrac{a+b+2c}{4}$ <br\/> Ta th\u1ea5y <br\/> $\\begin{align} & B-A=\\dfrac{a+b+2c}{4}-\\dfrac{a+b+c}{3} \\\\ & \\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,=\\dfrac{3a+3b+6c-4a-4b-4c}{12} \\\\ & \\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,=\\dfrac{-a-b+2c}{12} \\\\ & \\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,\\,=\\dfrac{\\left( c-a \\right)+\\left( c-b \\right)}{12}\\,\\,<0\\,\\,\\,(\\text{V\u00ec}\\,\\,\\,a > b > c) \\\\ & \\Rightarrow B < A \\\\ \\end{align}$ <br\/> V\u1eady c\u00e1ch t\u00ednh c\u1ee7a T\u00e2m cho k\u1ebft qu\u1ea3 nh\u1ecf h\u01a1n k\u1ebft qu\u1ea3 \u0111\u00fang. <br\/><span class='basic_pink'> V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B.<\/span><\/span>","column":3}]}],"id_ques":990}],"lesson":{"save":0,"level":3}}