{"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":[[["6"],["8"],["12"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.1a.png' \/><\/center>H\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 h\u00ecnh g\u1ed3m_input_m\u1eb7t, _input_ \u0111\u1ec9nh v\u00e0 _input_ c\u1ea1nh. ","hint":"","explain":"<span class='basic_left'>H\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 h\u00ecnh c\u00f3 $6$ m\u1eb7t, $8$ \u0111\u1ec9nh v\u00e0 $12$ c\u1ea1nh.<br\/><span class='basic_pink'>V\u1eady c\u00e1c s\u1ed1 c\u1ea7n \u0111i\u1ec1n l\u00e0 $6;8$ v\u00e0 $12$<\/span><\/span>"}]}],"id_ques":1810},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.1.png' \/><\/center>H\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 $6$ m\u1eb7t l\u00e0 c\u00e1c ","select":["A. H\u00ecnh thang","B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh b\u00ecnh h\u00e0nh","D. H\u00ecnh vu\u00f4ng"],"hint":"","explain":"<span class='basic_left'>H\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 $6$ m\u1eb7t l\u00e0 c\u00e1c h\u00ecnh ch\u1eef nh\u1eadt.<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B<\/span><\/span>","column":2}]}],"id_ques":1811},{"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/hinhhoc/bai20/lv1/img\/H8_B20_D1.2.png' \/><\/center>H\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 $6$ m\u1eb7t l\u00e0 c\u00e1c","select":["A. H\u00ecnh thang","B. H\u00ecnh ch\u1eef nh\u1eadt","C. H\u00ecnh b\u00ecnh h\u00e0nh","D. H\u00ecnh vu\u00f4ng"],"hint":"","explain":"<span class='basic_left'>H\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 $6$ m\u1eb7t l\u00e0 c\u00e1c h\u00ecnh vu\u00f4ng.<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":1812},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00fang hay sai","title_trans":"Cho h\u00ecnh v\u1ebd","temp":"true_false","correct":[["f","t","t","f","t"]],"list":[{"point":5,"image":"https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.4.png","col_name":["","\u0110\u00fang","Sai"],"arr_ques":["C\u00f3 $5$ \u0111i\u1ec3m n\u1eb1m trong m\u1eb7t ph\u1eb3ng $(P)$","\u0110i\u1ec3m $M$ n\u1eb1m ngo\u00e0i m\u1eb7t ph\u1eb3ng $(P)$","M\u1eb7t ph\u1eb3ng $(P)$ ch\u1ee9a \u0111\u01b0\u1eddng th\u1eb3ng $a$ v\u00e0 $b$","\u0110\u01b0\u1eddng th\u1eb3ng $c$ c\u1eaft \u0111\u01b0\u1eddng th\u1eb3ng $a$ t\u1ea1i $N$","Ba \u0111i\u1ec3m $A,\\, C,\\, N$ th\u1eb3ng h\u00e0ng."],"explain":[" Sai, tr\u00ean h\u00ecnh ch\u1ec9 c\u00f3 4 \u0111i\u1ec3m thu\u1ed9c m\u1eb7t ph\u1eb3ng $(P)$ l\u00e0 $A,B,C$ v\u00e0 $N$","<br\/> \u0110\u00fang. ","<br\/> \u0110\u00fang.","<br\/>Sai. V\u00ec \u0111\u01b0\u1eddng th\u1eb3ng $c$ c\u1eaft \u0111\u01b0\u1eddng th\u1eb3ng $b$ t\u1ea1i $N$","<br\/>\u0110\u00fang. V\u00ec $3$ \u0111i\u1ec3m c\u00f9ng thu\u1ed9c \u0111\u01b0\u1eddng th\u1eb3ng $b$."]}]}],"id_ques":1813},{"time":24,"part":[{"title":"\u0110i\u1ec1n t\u1eeb th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["A'C'","C'A'","a'c'","c'a'"]]],"list":[{"point":5,"width":150,"type_input":"","ques":"<span class='basic_left'>Cho h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt $ABCD.A\u2019B\u2019C\u2019D\u2019$. V\u1edbi $O$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $B\u2019D\u2019$. Khi \u0111\u00f3 $O$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a \u0111o\u1ea1n th\u1eb3ng n\u00e0o kh\u00e1c?<\/span><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.5.png' \/><\/center><br\/><b>Tr\u1ea3 l\u1eddi:<\/b> $O$ c\u00f2n l\u00e0 trung \u0111i\u1ec3m c\u1ee7a _input_","hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.5a.png' \/><\/center>V\u00ec h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt g\u1ed3m $6$ m\u1eb7t \u0111\u1ec1u l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt n\u00ean $A'B'C'D'$ c\u0169ng l\u00e0 h\u00ecnh ch\u1eef nh\u1eadt. <br\/>Suy ra $O$ l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $B'D'$ th\u00ec $O$ c\u0169ng l\u00e0 trung \u0111i\u1ec3m c\u1ee7a $A'C'$ (t\u00ednh ch\u1ea5t h\u00ecnh ch\u1eef nh\u1eadt)<br\/><span class='basic_pink'>V\u1eady c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $A'C'$<\/span><\/span>"}]}],"id_ques":1814},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"Cho h\u00ecnh v\u1ebd:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.3.png' \/><\/center><br\/>C\u00e1c c\u1ea1nh song song v\u1edbi c\u1ea1nh $AB$ l\u00e0:","select":["A. $DC$ v\u00e0 $D'C'$","B. $A'B',\\,D'C'$ v\u00e0 $AD$","C. $A'B',\\,D'C'$ v\u00e0 $DC$","D. $A'B',\\,D'C'$ v\u00e0 $AC$"],"hint":"","explain":" <span class='basic_left'>Hai \u0111\u01b0\u1eddng th\u1eb3ng song song l\u00e0 hai \u0111\u01b0\u1eddng th\u1eb3ng c\u00f9ng thu\u1ed9c m\u1ed9t m\u1eb7t ph\u1eb3ng v\u00e0 kh\u00f4ng c\u00f3 \u0111i\u1ec3m chung.<br\/>Hai \u0111\u01b0\u1eddng th\u1eb3ng ph\u00e2n bi\u1ec7t c\u00f9ng song song v\u1edbi \u0111\u01b0\u1eddng th\u1eb3ng th\u1ee9 ba th\u00ec song song v\u1edbi nhau.<br\/>V\u00ec v\u1eady, c\u00e1c c\u1ea1nh song song v\u1edbi $AB$ l\u00e0 $A'B',\\,D'C'$ <br\/>Ta c\u0169ng c\u00f3 $A'B'\/\/ DC$ v\u00ec c\u00f9ng song song v\u1edbi $D'C'$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C<\/span><br\/><b> Nh\u1eadn x\u00e9t: <\/b> Trong kh\u00f4ng gian v\u1edbi hai \u0111\u01b0\u1eddng th\u1eb3ng ph\u00e2n bi\u1ec7t, ch\u00fang c\u00f3 th\u1ec3: <br\/>- C\u1eaft nhau: Hai \u0111\u01b0\u1eddng th\u1eb3ng c\u00f3 m\u1ed9t \u0111i\u1ec3m chung.<br\/>- Song song: Hai \u0111\u01b0\u1eddng th\u1eb3ng c\u00f9ng thu\u1ed9c m\u1ed9t m\u1eb7t ph\u1eb3ng v\u00e0 kh\u00f4ng c\u00f3 \u0111i\u1ec3m chung<br\/>- Kh\u00f4ng c\u00f9ng n\u1eb1m m\u1ed9t m\u1eb7t ph\u1eb3ng.<\/span>","column":2}]}],"id_ques":1815},{"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":"Cho h\u00ecnh v\u1ebd:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.3.png' \/><\/center><br\/>M\u1eb7t ph\u1eb3ng song song v\u1edbi m\u1eb7t ph\u1eb3ng $ABB'A'$ l\u00e0:","select":["A. $DCC'D'$","B. $A'B'C'D'$","C. $ABDC$","D. $A'B'CD$"],"hint":"","explain":" <span class='basic_left'>Hai m\u1eb7t song song l\u00e0 hai m\u1eb7t ph\u1eb3ng kh\u00f4ng c\u00f3 \u0111i\u1ec3m chung.<br\/>V\u00ec v\u1eady, m\u1eb7t ph\u1eb3ng song song v\u1edbi $ABB'A'$ l\u00e0 $DCC'D'$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span><\/span>","column":2}]}],"id_ques":1816},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[2]],"list":[{"point":5,"ques":"Cho h\u00ecnh v\u1ebd:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.14.png' \/><\/center><br\/>Kh\u1eb3ng \u0111\u1ecbnh n\u00e0o sau \u0111\u00e2y l\u00e0 <b>sai<\/b>.","select":["A. $b\/\/mp(P)$","B. $a\\subset mp(P)$","C. $c\\subset mp(P)$","D. $a\\cap (P)$"],"hint":"","explain":" <span class='basic_left'>T\u1eeb h\u00ecnh v\u1ebd ta c\u00f3:<br\/>\u0110\u01b0\u1eddng th\u1eb3ng $a$ giao v\u1edbi m\u1eb7t ph\u1eb3ng $(P)$<br\/>\u0110\u01b0\u1eddng th\u1eb3ng $b$ song song v\u1edbi m\u1eb7t ph\u1eb3ng $(P)$<br\/>\u0110\u01b0\u1eddng th\u1eb3ng $c$ thu\u1ed9c m\u1eb7t ph\u1eb3ng $(P)$<br\/>V\u00ec v\u1eady, kh\u1eb3ng \u0111\u1ecbnh sai l\u00e0 $B$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n l\u00e0 B<\/span><br\/><b> Nh\u1eadn x\u00e9t: <\/b> V\u1edbi m\u1ed9t \u0111\u01b0\u1eddng th\u1eb3ng v\u00e0 m\u1eb7t ph\u1eb3ng trong kh\u00f4ng gian, ch\u00fang c\u00f3 th\u1ec3:<br\/>- C\u1eaft nhau: \u0110\u01b0\u1eddng th\u1eb3ng v\u00e0 m\u1eb7t ph\u1eb3ng c\u00f3 $1$ \u0111i\u1ec3m chung <br\/>- Song song v\u1edbi nhau: \u0110\u01b0\u1eddng th\u1eb3ng v\u00e0 m\u1eb7t ph\u1eb3ng kh\u00f4ng c\u00f3 \u0111i\u1ec3m chung<br\/>- \u0110\u01b0\u1eddng th\u1eb3ng thu\u1ed9c m\u1eb7t ph\u1eb3ng: \u0110\u01b0\u1eddng th\u1eb3ng v\u00e0 m\u1eb7t ph\u1eb3ng c\u00f3 v\u00f4 s\u1ed1 \u0111i\u1ec3m chung. <\/span>","column":2}]}],"id_ques":1817},{"time":24,"part":[{"time":3,"title":"N\u1ed1i c\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch v\u00e0 th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt","title_trans":"","audio":"","temp":"matching","correct":[["2","3","1"]],"list":[{"point":5,"image":"https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.6.png","left":["Di\u1ec7n t\u00edch xung quanh h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0","Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0","Th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0"],"right":["$abc$","$2c(a+b)$","$2(ab+bc+ca)$"],"top":100,"hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.6.png' \/><\/center>Ta c\u00f3:<br\/>- Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt b\u1eb1ng t\u1ed5ng di\u1ec7n t\u00edch c\u00e1c m\u1eb7t b\u00ean c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt: $2ca+2cb=2c(a+b)$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)<br\/>- Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt b\u1eb1ng t\u1ed5ng di\u1ec7n t\u00edch xung quanh v\u00e0 di\u1ec7n t\u00edch hai \u0111\u00e1y: $2(ab+bc+ca)$ (\u0111\u01a1n v\u1ecb di\u1ec7n t\u00edch)<br\/>- Th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 to\u00e0n b\u1ed9 kh\u00f4ng gian b\u00ean trong h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt: $abc$ (\u0111\u01a1n v\u1ecb th\u1ec3 t\u00edch)<br\/><\/span>"}]}],"id_ques":1818},{"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":[[["52"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"Cho h\u00ecnh v\u1ebd:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.7.png' \/><\/center><br\/>T\u00ednh di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt theo k\u00edch th\u01b0\u1edbc \u0111\u00e3 cho.<br\/><b> Tr\u1ea3 l\u1eddi: <\/b> _input_ ($cm^2$)","hint":"","explain":"<span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/>C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 $3$ k\u00edch th\u01b0\u1edbc l\u00e0 $a;b;c$ $(cm)$ l\u00e0: $S_{tp}=2(ab+bc+ca)\\,(cm^2)$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $2(2.3+3.4+2.4)=52$ ($cm^2$)<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $52$<\/span><\/span>"}]}],"id_ques":1819},{"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":[[["1014"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"T\u00ednh di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n h\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 \u0111\u1ed9 d\u00e0i c\u1ea1nh l\u00e0 $13\\,cm$.<br\/><b> Tr\u1ea3 l\u1eddi: <\/b> _input_ ($cm^2$)","hint":"","explain":"<span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/>C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 k\u00edch th\u01b0\u1edbc $a$ $(cm)$ l\u00e0: $S_{tp}=6a^2\\,(cm^2)$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.2a.png' \/><\/center>H\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 $6$ m\u1eb7t l\u00e0 c\u00e1c h\u00ecnh vu\u00f4ng c\u00f3 c\u1ea1nh $13\\,cm$ n\u00ean c\u00f3 di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n l\u00e0 $6.13^2=1014$ ($cm^2$)<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $1014$<\/span><\/span>"}]}],"id_ques":1820},{"time":24,"part":[{"title":"L\u1ef1a ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang nh\u1ea5t","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"ques":"<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/2.jpg' \/><\/center>Ph\u00f2ng ng\u1ee7 c\u1ee7a Lan d\u00e0i $3,5m$, r\u1ed9ng $3,2m$ v\u00e0 cao $2,5m$. Lan mu\u1ed1n mua gi\u1ea5y \u0111\u1ec3 d\u00e1n t\u01b0\u1eddng. H\u1ecfi Lan c\u1ea7n mua bao nhi\u00eau $m^2$ gi\u1ea5y. Bi\u1ebft t\u1ed5ng di\u1ec7n t\u00edch c\u1eeda l\u00e0 $4,5m^2$.","select":["A. $33,5m^2$","B. $44,8m^2$","C. $29m^2$","D. $39,3m^2$"],"hint":"Di\u1ec7n t\u00edch gi\u1ea5y c\u1ea7n mua $=$ Di\u1ec7n t\u00edch xung quanh $-$ Di\u1ec7n t\u00edch c\u1eeda.","explain":" <span class='basic_left'><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/>C\u00f4ng th\u1ee9c t\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u cao l\u00e0 $c\\,(cm)$, chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng \u0111\u00e1y l\u00e0 $a;\\,b\\,(cm)$ l\u00e0 $S_{tp}=2c(a+b)\\,(cm^2)$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>Di\u1ec7n t\u00edch xung quanh ph\u00f2ng ng\u1ee7 c\u1ee7a Lan t\u00ednh c\u1ea3 di\u1ec7n t\u00edch c\u1eeda l\u00e0: $2.2,5.(3,5+3,2)=33,5$ ($m^2$)<br\/>Di\u1ec7n t\u00edch gi\u1ea5y Lan ph\u1ea3i mua \u0111\u1ec3 d\u00e1n ph\u00f2ng l\u00e0 $33,5-4,5=29$ ($m^2$)<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C<\/span><\/span>","column":2}]}],"id_ques":1821},{"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":[[["15000"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"T\u00ednh th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt theo c\u00e1c k\u00edch th\u01b0\u1edbc \u0111\u00e3 cho \u1edf h\u00ecnh d\u01b0\u1edbi:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.8.png' \/><\/center><br\/><b> Tr\u1ea3 l\u1eddi: <\/b> Th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 _input_ ($cm^3$)","hint":"","explain":"<span class='basic_left'><br\/><span class='basic_green'>H\u01b0\u1edbng d\u1eabn<\/span><br\/>C\u00f4ng th\u1ee9c t\u00ednh th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u cao l\u00e0 $c\\,(cm)$, chi\u1ec1u r\u1ed9ng v\u00e0 chi\u1ec1u d\u00e0i \u0111\u00e1y l\u00e0 $a;\\,b\\,(cm)$ l\u00e0 $V=c.a.b\\,(cm^3)$<br\/><span class='basic_green'>B\u00e0i gi\u1ea3i<\/span><br\/>Th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $25.30.20=15000\\,(cm^3)$<br\/>V\u1eady h\u00ecnh h\u1ed9p c\u00f3 th\u1ec3 t\u00edch l\u00e0 $15000\\,cm^3$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $15000$<\/span><\/span>"}]}],"id_ques":1822},{"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":[[["125"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"T\u00ednh th\u1ec3 t\u00edch m\u1ed9t h\u00ecnh l\u1eadp ph\u01b0\u01a1ng. Bi\u1ebft n\u00f3 c\u00f3 di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n b\u1eb1ng di\u1ec7n t\u00edch xung quanh c\u1ee7a m\u1ed9t h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 chi\u1ec1u d\u00e0i l\u00e0 $8cm$, chi\u1ec1u r\u1ed9ng l\u00e0 $7cm$ v\u00e0 chi\u1ec1u cao l\u00e0 $5cm$.<br\/><b> Tr\u1ea3 l\u1eddi:<\/b>: _input_($cm^3$)","hint":"T\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt r\u1ed3i t\u00ednh c\u1ea1nh h\u00ecnh l\u1eadp ph\u01b0\u01a1ng.","explain":"<span class='basic_left'>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $2.5.(7+8)=150\\,(cm^2)$<br\/>V\u1eady di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh l\u1eadp ph\u01b0\u01a1ng l\u00e0 $150\\,cm^2$<br\/>Di\u1ec7n t\u00edch m\u1ed9t m\u1eb7t c\u1ee7a h\u00ecnh l\u1eadp ph\u01b0\u01a1ng l\u00e0 $150:6=25\\,(cm^2)$<br\/>\u0110\u1ed9 d\u00e0i m\u1ed9t c\u1ea1nh c\u1ee7a h\u00ecnh l\u1eadp ph\u01b0\u01a1ng l\u00e0 $a=\\sqrt{25}=5\\,(cm)$<br\/>V\u1eady th\u1ec3 t\u00edch h\u00ecnh l\u1eadp ph\u01b0\u01a1ng l\u00e0 $a^3=5^3=125\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $125$<\/span><\/span>"}]}],"id_ques":1823},{"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":[[["27"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<span class='basic_left'>Gi\u1ea3 s\u1eed m\u1ed7i kh\u1ed1i l\u1eadp ph\u01b0\u01a1ng nh\u1ecf trong kh\u1ed1i Rubik l\u00e0 $1\\,cm^3$.T\u00ednh th\u1ec3 t\u00edch c\u1ee7a kh\u1ed1i rubik k\u00edch th\u01b0\u1edbc $3$x$3$ nh\u01b0 h\u00ecnh v\u1ebd: <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.9.png' \/><\/center><br\/><br\/><b>Tr\u1ea3 l\u1eddi: <\/b> Th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 _input_ ($cm^3$)<\/span>","hint":"T\u00ednh s\u1ed1 kh\u1ed1i l\u1eadp ph\u01b0\u01a1ng nh\u1ecf.","explain":"<span class='basic_left'>Rubik c\u00f3 $3.3.3=27$ kh\u1ed1i l\u1eadp ph\u01b0\u01a1ng nh\u1ecf.<br\/>Do v\u1eady, th\u1ec3 t\u00edch c\u1ee7a kh\u1ed1i Rubik l\u00e0 $27.1=27\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $27$<\/span><\/span>"}]}],"id_ques":1824},{"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/hinhhoc/bai20/lv1/img\/H8_B20_D1.10.png' \/><\/center>T\u00ednh th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt $ABCD.A'B'C'D'$. Bi\u1ebft $AB=6\\,cm$, $BC=5\\,cm$ v\u00e0 $BC'=13\\,cm$.","select":["A. $360cm^3$","B. $390m^3$","C. $30m^3$","D. $120m^3$"],"hint":"T\u00ednh chi\u1ec1u cao $CC'$","explain":" <span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.10.png' \/><\/center>X\u00e9t tam gi\u00e1c $BCC'$ vu\u00f4ng t\u1ea1i $C$ c\u00f3 $BC'=13\\,cm$ v\u00e0 $BC=5\\,cm$<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago ta c\u00f3: <br\/>$BC'^2=BC^2+CC'^2\\\\ \\Leftrightarrow CC'=\\sqrt{BC'^2-BC^2}\\\\ \\Rightarrow CC'=\\sqrt{13^2-5^2}\\\\ \\Leftrightarrow CC'=\\sqrt{144}\\\\ \\Leftrightarrow CC'=12\\,(cm)$<br\/>V\u1eady th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt $ABCD.A'B'C'D'$ b\u1eb1ng $AB.BC.CC' =5.6.12=360\\,(cm^3)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A<\/span><\/span>","column":2}]}],"id_ques":1825},{"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/hinhhoc/bai20/lv1/img\/16.jpg' \/><\/center><span class='basic_left'>Cho h\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 th\u1ec3 t\u00edch l\u00e0 $512 cm^3$. M\u1ed9t h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 th\u1ec3 t\u00edch b\u1eb1ng th\u1ec3 t\u00edch h\u00ecnh l\u1eadp ph\u01b0\u01a1ng v\u00e0 chi\u1ec1u cao b\u1eb1ng \u0111\u1ed9 d\u00e0i c\u1ea1nh h\u00ecnh l\u1eadp ph\u01b0\u01a1ng. Chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng \u1edf \u0111\u00e1y t\u1ec9 l\u1ec7 v\u1edbi $4$ v\u00e0 $1$. T\u00ednh chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng \u1edf \u0111\u00e1y.<br\/>Chi\u1ec1u d\u00e0i v\u00e0 chi\u1ec1u r\u1ed9ng \u0111\u00e1y l\u1ea7n l\u01b0\u1ee3t l\u00e0:<\/span>","select":["A. $8\\,cm$ v\u00e0 $2\\,cm$","B. $4\\,cm$ v\u00e0 $1\\,cm$","C. $4\\,cm$ v\u00e0 $16\\,cm$","D. $16\\,cm$ v\u00e0 $4\\,cm$"],"hint":"","explain":" <span class='basic_left'>H\u00ecnh l\u1eadp ph\u01b0\u01a1ng c\u00f3 th\u1ec3 t\u00edch l\u00e0 $512\\,cm^3$ c\u00f3 \u0111\u1ed9 d\u00e0i c\u1ea1nh l\u00e0 $a=\\sqrt[3]{512}=8\\,(cm)$<br\/>Chi\u1ec1u cao c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $8\\,(cm)$<br\/>V\u00ec h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 th\u1ec3 t\u00edch b\u1eb1ng th\u1ec3 t\u00edch h\u00ecnh l\u1eadp ph\u01b0\u01a1ng n\u00ean th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $512\\,cm^3$<br\/>Di\u1ec7n t\u00edch \u0111\u00e1y h\u00ecnh l\u1eadp ph\u01b0\u01a1ng l\u00e0 $512:8=64\\,(cm)$<br\/>G\u1ecdi chi\u1ec1u r\u1ed9ng \u0111\u00e1y l\u00e0 $x$ ($cm,\\,x>0$)<br\/>V\u00ec chi\u1ec1u d\u00e0i \u0111\u00e1y v\u00e0 chi\u1ec1u r\u1ed9ng t\u1ec9 l\u1ec7 v\u1edbi $4$ v\u00e0 $1$ n\u00ean chi\u1ec1u d\u00e0i \u0111\u00e1y l\u00e0 $4x$ ($cm$)<br\/>Ta c\u00f3, di\u1ec7n t\u00edch \u0111\u00e1y l\u00e0 $64\\,cm^2$ n\u00ean: $x.4x=64\\,\\Leftrightarrow x^2=16\\,\\Leftrightarrow x=4$<br\/>V\u1eady chi\u1ec1u r\u1ed9ng \u0111\u00e1y l\u00e0 $4\\,cm$ v\u00e0 chi\u1ec1u d\u00e0i \u0111\u00e1y l\u00e0 $16\\,cm$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D<\/span><\/span>","column":2}]}],"id_ques":1826},{"time":24,"part":[{"title":"Ch\u1ecdn \u0111\u00e1p \u00e1n \u0111\u00fang","title_trans":"","temp":"multiple_choice","correct":[[3]],"list":[{"point":5,"select":["A. $10\\sqrt{2}$","B. $12\\sqrt{2}$","C. $15\\sqrt{2}$"],"ques":"<span class='basic_left'>Cho h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 k\u00edch th\u01b0\u1edbc nh\u01b0 h\u00ecnh v\u1ebd. T\u00ednh $AC\u2019$. <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.11.png' \/><\/center><br\/><b>Tr\u1ea3 l\u1eddi: <\/b> $AC'=$ ?($cm$)<\/span>","hint":"Tam gi\u00e1c $ABC'$ vu\u00f4ng t\u1ea1i $B$","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.11a.png' \/><\/center>Ta c\u00f3: $ABCD.A'B'C'D'$ l\u00e0 h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt n\u00ean $AB\\bot mp(BCC'B')$. Do \u0111\u00f3, $AB\\bot BC'$.<br\/>X\u00e9t tam gi\u00e1c $BCC'$ vu\u00f4ng t\u1ea1i $C$ c\u00f3 $BC=12\\,cm$ v\u00e0 $CC'=9\\,cm$<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago ta c\u00f3:<br\/>$BC'^2=BC^2+CC'^2\\\\ \\Leftrightarrow BC'=\\sqrt{BC^2+CC'^2}\\\\ \\Rightarrow BC'=\\sqrt{12^2+9^2}\\\\ \\Leftrightarrow BC'=\\sqrt{225}\\\\ \\Leftrightarrow BC'=15\\,(cm)$<br\/>X\u00e9t tam gi\u00e1c $ABC'$ vu\u00f4ng t\u1ea1i $B$ c\u00f3 $AB=15\\,cm$ v\u00e0 $BC'=15\\,cm$<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago ta c\u00f3:<br\/>$AC'^2=BC'^2+AB^2\\\\ \\Leftrightarrow AC'=\\sqrt{BC'^2+AB^2}\\\\ \\Rightarrow AC'=\\sqrt{15^2+15^2}\\\\ \\Leftrightarrow AC'=\\sqrt{2.15^2}\\\\ \\Leftrightarrow AC'=15\\sqrt {2}\\,(cm)$<\/span>"}]}],"id_ques":1827},{"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":[[["136"],["368"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt c\u00f3 k\u00edch th\u01b0\u1edbc \u0111\u00e1y l\u00e0 $40cm$ v\u00e0 $50 cm$, chi\u1ec1u cao l\u00e0 $35 cm$. Ng\u01b0\u1eddi ta x\u1ebfp v\u00e0o b\u00ean trong, c\u00e1c kh\u1ed1i l\u1eadp ph\u01b0\u01a1ng c\u00f3 k\u00edch th\u01b0\u1edbc $8 cm$. H\u1ecfi ng\u01b0\u1eddi ta x\u1ebfp \u0111\u01b0\u1ee3c bao nhi\u00eau h\u1ed9p v\u00e0 c\u00f2n bao nhi\u00eau kh\u00f4ng gian tr\u1ed1ng?<br\/><b> Tr\u1ea3 l\u1eddi: <\/b> X\u1ebfp \u0111\u01b0\u1ee3c s\u1ed1 h\u1ed9p l\u00e0_input_(h\u1ed9p);<br\/>C\u00f2n l\u1ea1i s\u1ed1 kh\u00f4ng gian tr\u1ed1ng l\u00e0 _input_ ($cm^3$)<\/span>","hint":"T\u00ednh th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh l\u1eadp ph\u01b0\u01a1ng v\u00e0 h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt","explain":"<span class='basic_left'>Th\u1ec3 t\u00edch h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0 $40.50.35=70000\\,(cm^3)$<br\/>Th\u1ec3 t\u00edch m\u1ed7i kh\u1ed1i l\u1eadp ph\u01b0\u01a1ng l\u00e0 $8^3=512\\,(cm^3)$<br\/>Ta c\u00f3: $70000:512=136$ d\u01b0 $368$.<br\/>Do \u0111\u00f3, ng\u01b0\u1eddi ta x\u1ebfp \u0111\u01b0\u1ee3c $136$ kh\u1ed1i l\u1eadp ph\u01b0\u01a1ng v\u00e0 c\u00f2n l\u1ea1i $368 cm^3$ kh\u00f4ng gian tr\u1ed1ng.<br\/><span class='basic_pink'>V\u1eady c\u00e1c s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $136$ v\u00e0 $368$<\/span><\/span>"}]}],"id_ques":1828},{"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":[[["2700"]]],"list":[{"point":5,"width":50,"type_input":"","ques":"<span class='basic_left'>Cho h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt $ABCD.A\u2019B\u2019C\u2019D\u2019$ c\u00f3 $AB:AD:AA\u2019=4:5:6$ v\u00e0 th\u1ec3 t\u00edch b\u1eb1ng $15000\\,cm^3$. T\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt.<br\/><b> Tr\u1ea3 l\u1eddi: <\/b> _input_ ($cm^2$)<\/span>","hint":"L\u1eadp t\u1ec9 s\u1ed1 c\u00e1c c\u1ea1nh v\u00e0 d\u00f9ng c\u00f4ng th\u1ee9c t\u00ednh th\u1ec3 t\u00edch \u0111\u1ec3 t\u00ecm c\u1ea1nh.","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop8/toan/hinhhoc/bai20/lv1/img\/H8_B20_D1.15.png' \/><\/center>Theo \u0111\u1ec1 b\u00e0i ta c\u00f3:<br\/>$AB:AD:AA\u2019=4:5:6\\Leftrightarrow \\dfrac{AB}{4}=\\dfrac{AD}{5}=\\dfrac{AA'}{6}=k\\,\\,(k>0)$<br\/>Suy ra $AB=4k;\\,AD=5k;\\,AA'=6k$<br\/>Ta c\u00f3: $V_{ABCD.A'B'C'D'}=AB.AD.AA'=4k.5k.6k=120k^3=15000\\\\ \\Leftrightarrow k^3=125\\\\ \\Leftrightarrow k=5\\,(\\text{(th\u1ecfa m\u00e3n)}$<br\/>V\u1eady $AB=20\\,cm;\\,AD=25\\,cm;\\,AA'=30\\,cm$<br\/>V\u1eady di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh h\u1ed9p ch\u1eef nh\u1eadt l\u00e0: $2.30.(25+20)=2700\\,(cm^2)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $2700$<\/span><\/span>"}]}],"id_ques":1829}],"lesson":{"save":0,"level":1}}