{"segment":[{"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":"<span class='basic_left'>Cho h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $R,$ di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u $S.$ Khi \u0111\u00f3: <\/span>","select":["A. $S=\\pi R^2$ ","B. $S=2\\pi R^2$ ","C. $S=4\\pi R^2$ "],"hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D1.png' \/><\/center><br\/>Di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u l\u00e0 $S=4\\pi R^2$<br\/>trong \u0111\u00f3:<br\/>$R:$ B\u00e1n k\u00ednh h\u00ecnh c\u1ea7u<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span> <\/span>","column":3}]}],"id_ques":1721},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["121"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>T\u00ednh di\u1ec7n t\u00edch c\u1ee7a m\u1ed9t m\u1eb7t c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $5,5$ $cm$ <br\/><b> \u0110\u00e1p s\u1ed1: <\/b> $S =$ _input_$\\pi $$(cm^2)$ ","hint":"","explain":"<span class='basic_left'>Di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u l\u00e0: <br\/>$S=4\\pi R^2=4\\pi .{5,5}^{2}=121\\pi \\left( c{{m}^{2}} \\right)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $121.$<\/span><\/span>"}]}],"id_ques":1722},{"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":"<span class='basic_left'>Cho h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $R,$ th\u1ec3 t\u00edch $V.$ Khi \u0111\u00f3: ","select":["A. $V=\\dfrac{1}{3}\\pi {{R}^{3}}$ ","B. $V=\\dfrac{4}{3}\\pi {{R}^{3}}$ ","C. $V=\\dfrac{2}{3}\\pi {{R}^{3}}$ "],"hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D1.png' \/><\/center><br\/>Th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0 $V=\\dfrac{4}{3}\\pi {{R}^{3}}$<br\/>trong \u0111\u00f3:<br\/>$R:$ B\u00e1n k\u00ednh h\u00ecnh c\u1ea7u<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span> <\/span>","column":3}]}],"id_ques":1723},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["21,8"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>T\u00ednh th\u1ec3 t\u00edch c\u1ee7a m\u1ed9t qu\u1ea3 b\u00f3ng c\u00f3 b\u00e1n k\u00ednh $\\sqrt{3}$ $cm$ (l\u00e0m tr\u00f2n \u0111\u1ebfn s\u1ed1 th\u1eadp ph\u00e2n th\u1ee9 nh\u1ea5t)<br\/><b> \u0110\u00e1p s\u1ed1: <\/b> $V \\approx $ _input_ $(cm^3)$ ","hint":"","explain":"<span class='basic_left'>Th\u1ec3 t\u00edch qu\u1ea3 b\u00f2ng l\u00e0: <br\/>$V=\\dfrac{4}{3}\\pi {{R}^{3}}=\\dfrac{4}{3}\\pi.(\\sqrt{3})^{3}=4\\sqrt{3}\\pi \\approx 21,8\\left( c{{m}^{3}} \\right)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $21,8.$<\/span><\/span>"}]}],"id_ques":1724},{"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":"<span class='basic_left'>B\u00e1n k\u00ednh c\u1ee7a m\u1ed9t h\u00ecnh c\u1ea7u t\u0103ng g\u1ea5p hai l\u1ea7n th\u00ec th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh c\u1ea7u \u0111o t\u0103ng g\u1ea5p b\u1ed1n l\u1ea7n, <b>\u0111\u00fang<\/b> hay <b>sai <\/b>? ","select":["A. \u0110\u00fang ","B. Sai "],"hint":"","explain":"<span class='basic_left'>X\u00e9t h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh ban \u0111\u1ea7u l\u00e0 $R$ th\u00ec th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0 $V=\\dfrac{4}{3}\\pi {{R}^{3}}$ <br\/>B\u00e1n k\u00ednh t\u0103ng g\u1ea5p hai l\u1ea7n th\u00ec th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0 $V'=\\dfrac{4}{3}\\pi {{\\left( 2R \\right)}^{3}}=8.\\dfrac{4}{3}\\pi {{R}^{3}}=8V$<br\/>V\u1eady th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u t\u0103ng g\u1ea5p $8$ l\u1ea7n.<br\/> Do \u0111\u00f3 kh\u1eb3ng \u0111\u1ecbnh tr\u00ean l\u00e0 sai<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n ch\u1ecdn l\u00e0 B.<\/span> <\/span>","column":2}]}],"id_ques":1725},{"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":"<span class='basic_left'>B\u00e1n k\u00ednh c\u1ee7a m\u1ed9t h\u00ecnh c\u1ea7u t\u0103ng g\u1ea5p $n$ l\u1ea7n th\u00ec th\u1ec3 t\u00edch t\u0103ng g\u1ea5p bao nhi\u00eau l\u1ea7n? ","select":["A. $n$ l\u1ea7n ","B. $n^2$ l\u1ea7n ","C. $2^n$ l\u1ea7n","D. $n^3$ l\u1ea7n"],"hint":"","explain":"<span class='basic_left'>X\u00e9t h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh ban \u0111\u1ea7u l\u00e0 $R$ th\u00ec th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0 $V=\\dfrac{4}{3}\\pi {{R}^{3}}$ <br\/>B\u00e1n k\u00ednh t\u0103ng g\u1ea5p $n$ l\u1ea7n th\u00ec th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0 $V'=\\dfrac{4}{3}\\pi {{\\left( nR \\right)}^{3}}={{n}^{3}}.\\dfrac{4}{3}\\pi {{R}^{3}}={{n}^{3}}V$<br\/>V\u1eady th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u t\u0103ng g\u1ea5p $n^3$ l\u1ea7n<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n ch\u1ecdn l\u00e0 D.<\/span><br\/><span class='basic_green'>Nh\u1eadn x\u00e9t:<\/span> N\u1ebfu b\u00e1n k\u00ednh c\u1ee7a h\u00ecnh c\u1ea7u t\u0103ng g\u1ea5p $n$ l\u1ea7n th\u00ec th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u t\u0103ng $n^3$ l\u1ea7n. <\/span>","column":4}]}],"id_ques":1726},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["64"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>B\u00e1n k\u00ednh Tr\u00e1i \u0110\u1ea5t g\u1ea5p kho\u1ea3ng $4$ l\u1ea7n b\u00e1n k\u00ednh M\u1eb7t Tr\u0103ng th\u00ec th\u1ec3 t\u00edch Tr\u00e1i \u0110\u1ea5t g\u1ea5p _input_ l\u1ea7n th\u1ec3 t\u00edch M\u1eb7t Tr\u0103ng <\/span>","hint":"","explain":"<span class='basic_left'>B\u00e1n k\u00ednh Tr\u00e1i \u0110\u1ea5t g\u1ea5p kho\u1ea3ng $4$ l\u1ea7n b\u00e1n k\u00ednh M\u1eb7t Tr\u0103ng th\u00ec th\u1ec3 t\u00edch Tr\u00e1i \u0110\u1ea5t g\u1ea5p $4^3 =64$ l\u1ea7n th\u1ec3 t\u00edch M\u1eb7t Tr\u0103ng<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $64.$<\/span><\/span>"}]}],"id_ques":1727},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["6"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh c\u1ea7u c\u00f3 s\u1ed1 \u0111o th\u1ec3 t\u00edch g\u1ea5p \u0111\u00f4i s\u1ed1 \u0111o di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u. T\u00ednh b\u00e1n k\u00ednh c\u1ee7a h\u00ecnh c\u1ea7u (\u0111\u01a1n v\u1ecb $cm$)<br\/><b>\u0110\u00e1p s\u1ed1:<\/b> _input_ $cm$","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh th\u1ec3 t\u00edch $V$ v\u00e0 di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u $S,$ ta gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh $V=2S$ \u0111\u1ec3 t\u00ecm b\u00e1n k\u00ednh","explain":"<span class='basic_left'>Gi\u1ea3 s\u1eed h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $R, $ di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u $S$ v\u00e0 th\u1ec3 t\u00edch $ V$<br\/>Do $V=2S$ n\u00ean<br\/>$\\begin{align} & \\,\\dfrac{4}{3}\\pi {{R}^{3}}=2.4\\pi {{R}^{2}} \\\\ & \\Leftrightarrow \\dfrac{R}{3}=2\\,\\,\\left( R\\ne 0 \\right) \\\\ & \\Leftrightarrow R=6\\left( cm \\right) \\\\ \\end{align}$<br\/> V\u1eady b\u00e1n k\u00ednh h\u00ecnh c\u1ea7u l\u00e0 $6cm$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $6$<\/span><\/span>"}]}],"id_ques":1728},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["3"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>T\u00ednh b\u00e1n k\u00ednh c\u1ee7a m\u1ed9t h\u00ecnh c\u1ea7u bi\u1ebft th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh c\u1ea7u b\u1eb1ng $113$ $dm^3$ (l\u00e0m tr\u00f2n \u0111\u1ebfn s\u1ed1 th\u1eadp ph\u00e2n th\u1ee9 nh\u1ea5t)<br\/><b>\u0110\u00e1p s\u1ed1:<\/b> _input_ $dm$<\/span>","hint":"\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c t\u00ednh th\u1ec3 t\u00edch $V,$ gi\u1ea3i ph\u01b0\u01a1ng tr\u00ecnh $V=113$ \u0111\u1ec3 t\u00ecm $R$","explain":"<span class='basic_left'>\u00c1p d\u1ee5ng c\u00f4ng th\u1ee9c $V=\\dfrac{4}{3}\\pi {{R}^{3}}$<br\/>Do $V=113$ ($dm^3$) n\u00ean <br\/>$\\begin{align} & \\dfrac{4}{3}\\pi {{R}^{3}}=113 \\\\ & \\Leftrightarrow {{R}^{3}}=\\dfrac{84,75}{\\pi } \\\\ & \\Rightarrow R\\approx 3\\left( dm \\right) \\\\ \\end{align}$ <br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $3.$<\/span><\/span>"}]}],"id_ques":1729},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["7,1"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>M\u1ed9t kh\u1ed1i s\u1eaft h\u00ecnh c\u1ea7u c\u00f3 \u0111\u01b0\u1eddng k\u00ednh $1,2$$dm.$ Bi\u1ebft $1$$dm^3$ s\u1eaft c\u00f3 kh\u1ed1i l\u01b0\u1ee3ng $7,87$$ kg.$ T\u00ednh kh\u1ed1i l\u01b0\u1ee3ng c\u1ee7a kh\u1ed1i s\u1eaft \u0111\u00f3. (l\u00e0m tr\u00f2n \u0111\u1ebfn s\u1ed1 th\u1eadp ph\u00e2n th\u1ee9 nh\u1ea5t)<br\/><b>\u0110\u00e1p s\u1ed1:<\/b> _input_$(kg)$<\/span>","hint":"","explain":"<span class='basic_left'>B\u00e1n k\u00ednh kh\u1ed1i s\u1eaft l\u00e0 $1,2:2=0,6$$ (dm)$<br\/>Th\u1ec3 t\u00edch kh\u1ed1i s\u1eaft l\u00e0 $\\dfrac{4}{3}\\pi .0,{{6}^{3}}\\approx 0,9\\left( d{{m}^{3}} \\right)$ <br\/>Kh\u1ed1i l\u01b0\u1ee3ng kh\u1ed1i s\u1eaft l\u00e0 $7,87.0,9\\approx 7,1\\left( kg \\right)$ <br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $7,1.$<\/span><\/span>"}]}],"id_ques":1730},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["121"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>Sao M\u1ed9c (h\u00e0nh tinh l\u1edbn nh\u1ea5t trong h\u1ec7 M\u1eb7t Tr\u1eddi) c\u00f3 \u0111\u01b0\u1eddng k\u00ednh g\u1ea5p kho\u1ea3ng $11$ l\u1ea7n \u0111\u01b0\u1eddng k\u00ednh Tr\u00e1i \u0110\u1ea5t. Di\u1ec7n t\u00edch b\u1ec1 m\u1eb7t sao M\u1ed9c g\u1ea5p kho\u1ea3ng bao nhi\u00eau l\u1ea7n b\u1ec1 m\u1eb7t Tr\u00e1i \u0110\u1ea5t?<br\/><b>\u0110\u00e1p s\u1ed1:<\/b> _input_ l\u1ea7n","hint":"","explain":"<span class='basic_left'>Gi\u1ea3 s\u1eed Tr\u00e1i \u0110\u1ea5t c\u00f3 b\u00e1n k\u00ednh $R.$ Suy ra \u0111\u01b0\u1eddng k\u00ednh Tr\u00e1i \u0110\u1ea5t l\u00e0 $2R$ v\u00e0 \u0111\u01b0\u1eddng k\u00ednh sao M\u1ed9c l\u00e0 $22R$<br\/>Suy ra b\u00e1n k\u00ednh sao M\u1ed9c l\u00e0 $11R$<br\/>Di\u1ec7n t\u00edch b\u1ec1 m\u1eb7t Tr\u00e1i \u0110\u1ea5t l\u00e0 ${{S}_{T\u0110}}=4\\pi {{R}^{2}}$ <br\/>Di\u1ec7n t\u00edch b\u1ec1 m\u1eb7t sao M\u1ed9c l\u00e0 ${{S}_{M}}=4\\pi {{\\left( 11R \\right)}^{2}}=121.\\left( 4\\pi {{R}^{2}} \\right)=121{{S}_{T\u0110}}$ <br\/>V\u1eady di\u1ec7n t\u00edch b\u1ec1 m\u1eb7t sao M\u1ed9c g\u1ea5p kho\u1ea3ng $121$ l\u1ea7n b\u1ec1 m\u1eb7t Tr\u00e1i \u0110\u1ea5t<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $121$<\/span><\/span>"}]}],"id_ques":1731},{"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":"<span class='basic_left'>Cho n\u1eeda h\u00ecnh c\u1ea7u t\u00e2m $O$ c\u00f3 $OR=a$ $(cm), $$\\widehat{TOS}={{60}^{o}}$. <br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D2.png' \/><\/center><br\/>\u0110\u1ed9 d\u00e0i $ST$ nh\u1eadn gi\u00e1 tr\u1ecb n\u00e0o trong c\u00e1c gi\u00e1 tr\u1ecb sau: ","select":["A. $a\\sqrt{3}$$(cm)$","B. $\\dfrac{a\\sqrt{3}}{2}$$(cm)$","C. $\\dfrac{a}{2}$$(cm)$"],"hint":"","explain":"<span class='basic_left'>X\u00e9t tam gi\u00e1c vu\u00f4ng $SOT$ c\u00f3 $OS=OR=a$ $(cm)$ v\u00e0 $\\widehat{TOS}={{60}^{o}}$<br\/>Suy ra $ST=SO.sin{\\widehat{TOS}}=a.sin{60^o}=$$\\dfrac{a\\sqrt{3}}{2}$ $(cm)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 B.<\/span> <\/span>","column":3}]}],"id_ques":1732},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o \u00f4 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["33"]]],"list":[{"point":5,"width":60,"type_input":"","ques":"<span class='basic_left'>H\u00ecnh g\u1ed3m m\u1ed9t n\u1eeda h\u00ecnh c\u1ea7u v\u00e0 m\u1ed9t h\u00ecnh n\u00f3n.<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D3.png' \/><\/center><br\/> Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh b\u1eb1ng _input_$\\pi $$(cm^2)$ <\/span>","hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D3a.png' \/><\/center><br\/>X\u00e9t $\\Delta OAB$ vu\u00f4ng t\u1ea1i $O.$ \u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00ed Pytago, ta c\u00f3:<br\/>$A{{B}^{2}}=O{{A}^{2}}+O{{B}^{2}}={{4}^{2}}+{{3}^{2}}=25\\Rightarrow AB=5$ $(cm)$<br\/>H\u00ecnh n\u00f3n c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $3$$cm,$ \u0111\u01b0\u1eddng sinh l\u00e0 $5$ $cm$ n\u00ean c\u00f3 di\u1ec7n t\u00edch xung quanh l\u00e0 <br\/>${{S}_{1}}=\\pi .3.5=15\\pi \\left( c{{m}^{2}} \\right)$ <br\/>H\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $3$$cm $ n\u00ean di\u1ec7n t\u00edch b\u1ec1 m\u1eb7t n\u1eeda h\u00ecnh c\u1ea7u l\u00e0:<br\/> ${{S}_{2}}=2\\pi {{.3}^{2}}=18\\pi \\left( c{{m}^{2}} \\right)$ <br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh l\u00e0:<br\/>${{S}_{xq}}={{S}_{1}}+{{S}_{2}}=15\\pi +18\\pi =33\\pi \\left( c{{m}^{2}} \\right)$<br\/><span class='basic_pink'>V\u1eady s\u1ed1 c\u1ea7n \u0111i\u1ec1n v\u00e0o \u00f4 tr\u1ed1ng l\u00e0 $33.$<\/span><\/span>"}]}],"id_ques":1733},{"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":"<span class='basic_left'>Chi\u1ec1u cao c\u1ee7a m\u1ed9t h\u00ecnh tr\u1ee5 g\u1ea5p r\u01b0\u1ee1i b\u00e1n k\u00ednh \u0111\u00e1y c\u1ee7a n\u00f3. T\u1ec9 s\u1ed1 th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh tr\u1ee5 n\u00e0y v\u00e0 th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh b\u1eb1ng b\u00e1n k\u00ednh \u0111\u00e1y c\u1ee7a h\u00ecnh tr\u1ee5 l\u00e0:","select":["A. $\\dfrac{3}{2}$","B. $\\dfrac{2}{3}$","C. $\\dfrac{8}{9}$","D. $\\dfrac{9}{8}$"],"hint":"","explain":"<span class='basic_left'>Gi\u1ea3 s\u1eed h\u00ecnh tr\u1ee5 c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y $R.$ Suy ra chi\u1ec1u cao c\u1ee7a n\u00f3 l\u00e0 $1,5R.$<br\/>Th\u1ec3 t\u00edch h\u00ecnh tr\u1ee5 l\u00e0 ${{V}_{1}}=\\pi {{R}^{2}}h=\\pi {{R}^{2}}.1,5R=1,5\\pi {{R}^{3}}$ <br\/>Th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $R$ l\u00e0 ${{V}_{2}}=\\dfrac{4}{3}\\pi {{R}^{3}}$ <br\/>$\\Rightarrow \\dfrac{{{V}_{1}}}{{{V}_{2}}}=\\dfrac{1,5\\pi {{R}^{3}}}{\\dfrac{4}{3}\\pi {{R}^{3}}}=\\dfrac{9}{8}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 D.<\/span> <\/span>","column":2}]}],"id_ques":1734},{"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":"<span class='basic_left'>M\u1ed9t h\u00ecnh c\u1ea7u b\u00e1n k\u00ednh $R $$(cm)$ \u0111\u01b0\u1ee3c \u0111\u1eb7t v\u00e0o trong m\u1ed9t h\u00ecnh tr\u1ee5 c\u00f3 chi\u1ec1u cao $2,5R$$ (cm) $ nh\u01b0 h\u00ecnh v\u1ebd:<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D4.png' \/><\/center><br\/>T\u1ec9 s\u1ed1 $\\dfrac{V_{\\text{c\u1ea7u}}}{V_{\\text{tr\u1ee5}}}$ b\u1eb1ng","select":["A. $\\dfrac{5}{2}$","B. $\\dfrac{4}{5}$","C. $\\dfrac{8}{15}$","D. $\\dfrac{15}{8}$"],"hint":"","explain":"<span class='basic_left'>Th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0 ${{V}_{c\u1ea7u}}=\\dfrac{4}{3}\\pi {{R}^{3}}\\left( c{{m}^{3}} \\right)$<br\/>Th\u1ec3 t\u00edch h\u00ecnh tr\u1ee5 l\u00e0 ${{V}_{tr\u1ee5}}=\\pi {{R}^{2}}h=\\pi {{R}^{2}}.2,5R=2,5\\pi {{R}^{3}}$ $(cm^3)$<br\/>Suy ra $\\dfrac{V_{\\text{c\u1ea7u}}}{V_{\\text{tr\u1ee5}}}=\\dfrac{\\dfrac{4}{3}\\pi {{R}^{3}}}{2,5\\pi {{R}^{3}}}=\\dfrac{8}{15}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 C.<\/span> <\/span>","column":4}]}],"id_ques":1735},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o c\u00e1c ch\u1ed7 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["400"],["4000"],["3"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh tr\u1ee5 \u0111\u01b0\u1ee3c \u0111\u1eb7t kh\u00edt b\u00ean trong m\u1ed9t h\u00ecnh c\u1ea7u \u0111\u01b0\u1eddng k\u00ednh $20$$cm.$<br\/><b> C\u00e2u a: <\/b> T\u00ednh di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u v\u00e0 th\u1ec3 t\u00edch m\u1eb7t c\u1ea7u. (\u0110i\u1ec1n k\u1ebft qu\u1ea3 \u1edf d\u1ea1ng t\u1ed1i gi\u1ea3n nh\u1ea5t)<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D5.png' \/><\/center><br\/><b>\u0110\u00e1p s\u1ed1:<\/b> $S=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\pi$ $(cm^2);$ $V=\\frac{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}\\pi$ $(cm^3)$<\/span>","hint":"","explain":"<span class='basic_left'>H\u00ecnh c\u1ea7u c\u00f3 \u0111\u01b0\u1eddng k\u00ednh $20$$cm$ n\u00ean b\u00e1n k\u00ednh b\u1eb1ng $10$$cm$<br\/>Di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u l\u00e0 $S=4\\pi {{R}^{2}}=4\\pi {{.10}^{2}}=400\\pi \\left( c{{m}^{2}} \\right)$ <br\/>Th\u1ec3 t\u00edch m\u1eb7t c\u1ea7u l\u00e0 $V=\\dfrac{4}{3}\\pi {{R}^{3}}=\\dfrac{4}{3}\\pi {{.10}^{3}}=\\dfrac{4000}{3}\\pi \\left( c{{m}^{3}} \\right)$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t l\u00e0 $400;$$4000;$$3.$ <\/span><\/span>"}]}],"id_ques":1736},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["200"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'>M\u1ed9t h\u00ecnh tr\u1ee5 \u0111\u01b0\u1ee3c \u0111\u1eb7t kh\u00edt b\u00ean trong m\u1ed9t h\u00ecnh c\u1ea7u \u0111\u01b0\u1eddng k\u00ednh $20$$cm.$<br\/><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D5.png' \/><\/center><br\/><b> C\u00e2u b: <\/b> T\u00ednh di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh tr\u1ee5 bi\u1ebft chi\u1ec1u cao c\u1ee7a h\u00ecnh tr\u1ee5 b\u1eb1ng \u0111\u01b0\u1eddng k\u00ednh \u0111\u00e1y c\u1ee7a n\u00f3.<br\/><b>\u0110\u00e1p s\u1ed1:<\/b> $S_{xq}=\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}\\pi$ $(cm^2)$<\/span>","hint":"","explain":"<span class='basic_left'><center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D5a.png' \/><\/center>Chi\u1ec1u cao c\u1ee7a h\u00ecnh tr\u1ee5 b\u1eb1ng \u0111\u01b0\u1eddng k\u00ednh \u0111\u00e1y c\u1ee7a h\u00ecnh tr\u1ee5 n\u00ean $AB=AC$<br\/>$\\Delta{ABC}$ c\u00f3 $O$ l\u00e0 trung \u0111i\u1ec3m $BC$ v\u00e0 $AO=\\dfrac{BC}{2}$ n\u00ean $\\Delta{ABC}$ vu\u00f4ng t\u1ea1i $A$.<br\/>\u00c1p d\u1ee5ng \u0111\u1ecbnh l\u00fd Pytago, ta c\u00f3: <br\/>$AB^2+AC^2=BC^2 \\Leftrightarrow 2AB^2=BC^2$<br\/>$ \\Rightarrow 2AB^2=20^2 \\Rightarrow AB=10 \\sqrt{2}$$(cm).$<br\/>Suy ra h\u00ecnh tr\u1ee5 c\u00f3 chi\u1ec1u cao l\u00e0 $10 \\sqrt{2}$ $cm$ v\u00e0 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $5 \\sqrt{2}$$cm$<br\/>Di\u1ec7n t\u00edch xung quanh c\u1ee7a h\u00ecnh tr\u1ee5 l\u00e0 <br\/>$S=2\\pi Rh=2\\pi .5 \\sqrt{2}.10 \\sqrt{2}=200\\pi \\left( c{{m}^{2}} \\right)$<br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u00e0 $200.$ <\/span><\/span>"}]}],"id_ques":1737},{"time":24,"part":[{"title":"\u0110i\u1ec1n k\u1ebft qu\u1ea3 th\u00edch h\u1ee3p v\u00e0o c\u00e1c ch\u1ed7 tr\u1ed1ng","title_trans":"","temp":"fill_the_blank","correct":[[["60"],["40"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'>Cho m\u1ed9t h\u00ecnh tr\u1ee5, m\u1ed9t h\u00ecnh n\u00f3n v\u00e0 m\u1ed9t h\u00ecnh c\u1ea7u, trong \u0111\u00f3 h\u00ecnh tr\u1ee5 v\u00e0 h\u00ecnh n\u00f3n c\u00f3 \u0111\u01b0\u1eddng k\u00ednh \u0111\u00e1y v\u00e0 chi\u1ec1u cao b\u1eb1ng \u0111\u01b0\u1eddng k\u00ednh c\u1ee7a h\u00ecnh c\u1ea7u. Bi\u1ebft th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n b\u1eb1ng $20$$cm^3. $T\u00ednh th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh tr\u1ee5 v\u00e0 h\u00ecnh c\u1ea7u.<br\/><b>\u0110\u00e1p s\u1ed1:<\/b> $V_\\text{tr\u1ee5}=$_input_$(cm^3)$; $V_\\text{c\u1ea7u}=$_input_$(cm^3)$<\/span>","hint":"","explain":"<span class='basic_left'>H\u00ecnh tr\u1ee5 v\u00e0 h\u00ecnh n\u00f3n c\u00f3 \u0111\u01b0\u1eddng k\u00ednh \u0111\u00e1y v\u00e0 chi\u1ec1u cao b\u1eb1ng \u0111\u01b0\u1eddng k\u00ednh c\u1ee7a h\u00ecnh c\u1ea7u n\u00ean ch\u00fang c\u00f3 c\u00f9ng b\u00e1n k\u00ednh<br\/>G\u1ecdi b\u00e1n k\u00ednh \u0111\u00e1y c\u1ee7a h\u00ecnh tr\u1ee5, h\u00ecnh n\u00f3n v\u00e0 b\u00e1n k\u00ednh h\u00ecnh c\u1ea7u l\u00e0 $R$ $(cm)$<br\/>H\u00ecnh n\u00f3n v\u00e0 h\u00ecnh tr\u1ee5 c\u00f3 chi\u1ec1u cao b\u1eb1ng $2R$ $(cm)$<br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh tr\u1ee5 l\u00e0 $V_\\text{tr\u1ee5}=\\pi {{R}^{2}}.2R=2\\pi {{R}^{3}}$ $(cm^3)$<br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh n\u00f3n l\u00e0 $V_\\text{n\u00f3n}=\\dfrac{1}{3}\\pi {{R}^{2}}.2R=\\dfrac{2}{3}\\pi {{R}^{3}}$ $(cm^3)$<br\/>Th\u1ec3 t\u00edch c\u1ee7a h\u00ecnh c\u1ea7u l\u00e0 $V_\\text{c\u1ea7u}=\\dfrac{4}{3}\\pi {{R}^{3}}$ $(cm^3)$<br\/>Ta c\u00f3 $V_\\text{n\u00f3n}=\\dfrac{V_\\text{tr\u1ee5}}{3}\\Rightarrow V_{\\text{tr\u1ee5}}=3V_{\\text{n\u00f3n}}=3.20=60\\left( c{{m}^{3}} \\right)$ <br\/>$V_{\\text{c\u1ea7u}}=2V_{\\text{n\u00f3n}}=2.20=40\\left( cm^3 \\right)$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t l\u00e0 $60;$ $40.$ <\/span><\/span>"}]}],"id_ques":1738},{"time":24,"part":[{"title":"\u0110i\u1ec1n s\u1ed1 th\u00edch h\u1ee3p v\u00e0o ch\u1ed7 tr\u1ed1ng","title_trans":"\u0110\u1ec1 chung cho hai c\u00e2u","temp":"fill_the_blank","correct":[[["2"],["3"]]],"list":[{"point":5,"width":40,"content":"","type_input":"","ques":"<span class='basic_left'>H\u00ecnh v\u1ebd sau m\u00f4 t\u1ea3 m\u1ed9t h\u00ecnh c\u1ea7u n\u1ed9i ti\u1ebfp m\u1ed9t h\u00ecnh tr\u1ee5 (t\u1ee9c h\u00ecnh c\u1ea7u \u0111\u1eb7t kh\u00edt v\u00e0o trong h\u00ecnh tr\u1ee5).<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D6.png' \/><\/center><br\/><b>C\u00e2u a:<\/b> T\u1ec9 s\u1ed1 gi\u1eefa di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u v\u00e0 di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a m\u1ed9t h\u00ecnh tr\u1ee5 b\u1eb1ng $\\frac{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}{\\FormInput[40][bl_elm_true basic_elm basic_blank basic_blank_part]{}}$<br\/>(\u0110\u00e1p \u00e1n \u0111i\u1ec1n d\u01b0\u1edbi d\u1ea1ng ph\u00e2n s\u1ed1 t\u1ed1i gi\u1ea3n) <\/span>","hint":"","explain":"<span class='basic_left'>Gi\u1ea3 s\u1eed h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $R.$ Suy ra h\u00ecnh tr\u1ee5 c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $R,$ \u0111\u01b0\u1eddng sinh $2R$<br\/>Ta c\u00f3 di\u1ec7n t\u00edch m\u1eb7t c\u1ea7u l\u00e0 $S_{\\text{c\u1ea7u}}=4\\pi {{R}^{2}}$ <br\/>Di\u1ec7n t\u00edch to\u00e0n ph\u1ea7n c\u1ee7a h\u00ecnh tr\u1ee5 l\u00e0: $S_{\\text{tr\u1ee5}}=2\\pi R.2R+2\\pi {{R}^{2}}=6\\pi {{R}^{2}}$ <br\/>Suy ra $\\dfrac{S_{\\text{c\u1ea7u}}}{S_{\\text{tr\u1ee5}}}=\\dfrac{4\\pi {{R}^{2}}}{6\\pi {{R}^{2}}}=\\dfrac{2}{3}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n c\u1ea7n \u0111i\u1ec1n l\u1ea7n l\u01b0\u1ee3t l\u00e0 $2$ v\u00e0 $ 3.$ <\/span><\/span>"}]}],"id_ques":1739},{"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":[[1]],"list":[{"point":5,"ques":"<span class='basic_left'>H\u00ecnh v\u1ebd sau m\u00f4 t\u1ea3 m\u1ed9t h\u00ecnh c\u1ea7u n\u1ed9i ti\u1ebfp m\u1ed9t h\u00ecnh tr\u1ee5 (t\u1ee9c h\u00ecnh c\u1ea7u \u0111\u1eb7t kh\u00edt v\u00e0o trong h\u00ecnh tr\u1ee5).<center><img src='https://www.luyenthi123.com/file/luyenthi123/lop9/toan/hinhhoc/bai24/lv1/img\/H943_D6.png' \/><\/center><br\/><b>C\u00e2u b:<\/b> Hi\u1ec7u gi\u1eefa th\u1ec3 t\u00edch h\u00ecnh tr\u1ee5 v\u00e0 th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u b\u1eb1ng:","select":["A. $\\dfrac{2}{3}\\pi {{R}^{3}}$ ","B. $\\dfrac{1}{3}\\pi {{R}^{3}}$ ","C. $\\dfrac{3}{4}\\pi {{R}^{3}}$ "],"hint":"","explain":"<span class='basic_left'>Gi\u1ea3 s\u1eed h\u00ecnh c\u1ea7u c\u00f3 b\u00e1n k\u00ednh $R.$ <br\/>Suy ra h\u00ecnh tr\u1ee5 c\u00f3 b\u00e1n k\u00ednh \u0111\u00e1y l\u00e0 $R,$ \u0111\u01b0\u1eddng cao $2R$<br\/>Th\u1ec3 t\u00edch h\u00ecnh tr\u1ee5 l\u00e0 ${{V}_{tr\u1ee5}}=\\pi {{R}^{2}}\\left( 2R \\right)=2\\pi {{R}^{3}}$ <br\/>Th\u1ec3 t\u00edch m\u1eb7t c\u1ea7u l\u00e0 ${{V}_{c\u1ea7u}}=\\dfrac{4}{3}\\pi {{R}^{3}}$<br\/>Hi\u1ec7u gi\u1eefa th\u1ec3 t\u00edch h\u00ecnh tr\u1ee5 v\u00e0 th\u1ec3 t\u00edch h\u00ecnh c\u1ea7u l\u00e0:<br\/>${{V}_{tr\u1ee5}}-{{V}_{c\u1ea7u}}=2\\pi {{R}^{3}}-\\dfrac{4}{3}\\pi {{R}^{3}}=\\dfrac{2}{3}\\pi {{R}^{3}}$ <br\/><span class='basic_pink'>V\u1eady \u0111\u00e1p \u00e1n \u0111\u00fang l\u00e0 A.<\/span> <\/span>","column":3}]}],"id_ques":1740}],"lesson":{"save":0,"level":1}}