{"id":25443,"date":"2021-12-24T16:47:00","date_gmt":"2021-12-24T09:47:00","guid":{"rendered":"https:\/\/www.vietlearn.org\/post\/?p=25443"},"modified":"2021-12-24T16:47:01","modified_gmt":"2021-12-24T09:47:01","slug":"bai-so-3-do-vui-luyen-tri-thong-minh","status":"publish","type":"post","link":"https:\/\/www.vietlearn.org\/kien-thuc\/bai-so-3-do-vui-luyen-tri-thong-minh\/","title":{"rendered":"B\u00c0I S\u1ed0 3 – \u0110\u1ed1 vui luy\u1ec7n tr\u00ed th\u00f4ng minh"},"content":{"rendered":"

<\/a>C\u00c2U 1:<\/h3>\n

\u0110i\u1ec1n ti\u1ebfp v\u00e0o d\u1ea5u (?).<\/p>\n

\"8_2.jpg\"<\/p>\n

<\/a>C\u00c2U 2:<\/h3>\n

\u0110i\u1ec1n ti\u1ebfp v\u00e0o d\u1ea5u (?).<\/p>\n

\"9_1.jpg\"<\/p>\n

<\/a>C\u00c2U 3:<\/h3>\n

T\u1eeb m\u1ed9t t\u1edd gi\u1ea5y k\u1ebb \u00f4 vu\u00f4ng, b\u1ea1n khang c\u1eaft ra m\u1ed9t h\u00ecnh sao b\u1ed1n c\u00e1nh nh\u01b0 h\u00ecnh d\u01b0\u1edbi. H\u1ecfi h\u00ecnh sao n\u00e0y c\u00f3 di\u1ec7n T\u00edch b\u1eb1ng m\u1ea5y \u00f4 vu\u00f4ng?<\/p>\n

\"9_2.jpg\"<\/p>\n

<\/a>C\u00c2U 4:<\/h3>\n

Nh\u00e0 kia c\u00f3 hai v\u1ee3 ch\u1ed3ng, 6 \u0111\u1ee9a con g\u00e1i, m\u1ed7i ng\u01b0\u1eddi con g\u00e1i c\u00f3 1 em trai. H\u1ecfi t\u1ed5ng c\u1ed9ng c\u00f3 bao nhi\u00eau ng\u01b0\u1eddi?<\/p>\n

<\/a>C\u00c2U 5:<\/h3>\n

V\u1eeba g\u00e0 v\u1eeba ch\u00f3<\/p>\n

B\u00f3 l\u1ea1i cho tr\u00f2n<\/p>\n

Ba m\u01b0\u01a1i s\u00e1u con<\/p>\n

M\u1ed9t tr\u0103m ch\u00e2n ch\u1eb5n.<\/p>\n

H\u1ecfi c\u00f3 bao nhi\u00eau g\u00e0, bao nhi\u00eau ch\u00f3?<\/p>\n

H\u01af\u1edaNG D\u1eaaN – B\u00c0I GI\u1ea2I – \u0110\u00c1P S\u1ed0<\/h1>\n

<\/a>B\u00c0I S\u1ed0 3<\/h2>\n

<\/a>C\u00c2U 1:<\/h3>\n

C\u00e1ch 1:<\/p>\n

3 = 1 x 1 x 3<\/p>\n

12 = 2 x 2 x 3<\/p>\n

27 = 3 x 3 x 3<\/p>\n

75 = 5 x 5 x 3<\/p>\n

Ta c\u00f3 \u0111\u00e1p s\u1ed1: 48 = 4 x 4 x 3<\/p>\n

C\u00e1ch 2:<\/p>\n

\"95.jpg\"<\/p>\n

C\u00e1ch 3:<\/p>\n

\"96_1.jpg\"<\/p>\n

<\/a>C\u00c2U 2:<\/h3>\n

\u0110\u00e1p s\u1ed1 1:<\/p>\n

6 = 1 x 2 x 3<\/p>\n

24 = 2 x 3 x 4<\/p>\n

60 = 3 x 4 x 5<\/p>\n

120 = 4 x 5 x 6.<\/p>\n

\u0110\u00e1p s\u1ed1: 60.<\/p>\n

\u0110\u00e1p s\u1ed1 2:<\/p>\n

\"96_2.jpg\"<\/p>\n

\u0110\u00e1p s\u1ed1 3:<\/p>\n

\"97_1.jpg\"<\/p>\n

<\/a>C\u00c2U 3:<\/h3>\n

B\u00e0i gi\u1ea3i:<\/p>\n

C\u00f3 nhi\u1ec1u c\u00e1ch l\u00e0m, xin gi\u1edbi thi\u1ec7u 2 c\u00e1ch \u0111\u1ec3 c\u00e1c b\u1ea1n tham kh\u1ea3o.<\/p>\n

C\u00e1ch 1: Di\u1ec7n t\u00edch h\u00ecnh sao \u0111\u00fang b\u1eb1ng di\u1ec7n t\u00edch h\u00ecnh vu\u00f4ng g\u1ed3m 16 \u00f4 vu\u00f4ng tr\u1eeb \u0111i di\u1ec7n t\u00edch 4 h\u00ecnh tam gi\u00e1c b\u1eb1ng nhau. M\u1ed7i tam gi\u00e1c n\u00e0y c\u00f3 di\u1ec7n t\u00edch l\u00e0 2 \u00f4 vu\u00f4ng. Do \u0111\u00f3 di\u1ec7n t\u00edch h\u00ecnh sao l\u00e0: 16 – (2 x 4) = 8 (\u00f4 vu\u00f4ng).<\/p>\n

\"97_2.jpg\"<\/p>\n

C\u00e1ch 2:<\/p>\n

C\u1eaft gh\u00e9p \u0111\u1ec3 t\u1eeb h\u00ecnh sao ta c\u00f3 h\u00ecnh m\u1edbi m\u00e0 h\u00ecnh n\u00e0y di\u1ec7n t\u00edch \u0111\u00fang b\u1eb1ng 8 \u00f4 vu\u00f4ng.<\/p>\n

\"98.jpg\"<\/p>\n

<\/a>C\u00c2U 4:<\/h3>\n

\u0110\u00e1p s\u1ed1:<\/p>\n

2 v\u1ee3 ch\u1ed3ng + 6 con g\u00e1i + 1 m\u1ed9t trai \u00fat = 9 ng\u01b0\u1eddi.<\/p>\n

<\/a>C\u00c2U 5:<\/h3>\n

B\u00e0i gi\u1ea3i:<\/p>\n

Gi\u1ea3i theo ph\u01b0\u01a1ng ph\u00e1p gi\u1ea3 thi\u1ebft t\u1ea1m (gi\u1ea3 thi\u1ebft t\u1ea1m l\u00e0 nh\u1eefng \u0111i\u1ec1u ta t\u01b0\u1edfng t\u01b0\u1ee3ng ra \u0111\u1ec3 gi\u00fap cho vi\u1ec7c gi\u1ea3i to\u00e1n \u0111\u01b0\u1ee3c d\u1ec5 d\u00e0ng. Ch\u1eef \u201ct\u1ea1m\u201d \u1edf \u0111\u00e2y ng\u1ee5 \u00fd \u201cnh\u1eefng \u0111i\u1ec1u m\u00e0 ta t\u01b0\u1edfng t\u01b0\u1ee3ng ra \u1ea5y ch\u1ec9 c\u00f3 \u00fd ngh\u0129a nh\u1ea5t th\u1eddi, l\u00fac gi\u1ea3i to\u00e1n th\u00ec ta c\u1ea7n \u0111\u1ebfn ch\u00fang, khi gi\u1ea3i xong th\u00ec c\u00f3 th\u1ec3 qu\u00ean ch\u00fang \u0111i\u201d.<\/p>\n

C\u00e1ch 1:<\/p>\n

Gi\u1ea3 s\u1eed m\u1ed7i con ch\u00f3 \u0111\u1ec1u ch\u1ec9 \u0111\u1ee9ng b\u1eb1ng hai ch\u00e2n sau v\u00e0 co hai ch\u00e2n tr\u01b0\u1edbc l\u00ean (gi\u1ed1ng nh\u01b0 con ch\u00f3 l\u00e0m xi\u1ebfc v\u1eady) th\u1ebf th\u00ec m\u1ed7i con ch\u00f3 \u0111\u1ec1u ch\u1ec9 c\u00f3 hai ch\u00e2n v\u00e0 ta c\u00f3 th\u1ec3 coi 36 con \u0111\u1ec1u l\u00e0 g\u00e0 c\u1ea3.<\/p>\n

L\u00fac \u0111\u00f3 36 con c\u00f3:<\/p>\n

36 x 2 = 72 (ch\u00e2n)<\/p>\n

V\u1eady s\u1ed1 ch\u00e2n co l\u00ean l\u00e0:<\/p>\n

100 \u2013 72 = 28 (ch\u00e2n)<\/p>\n

Suy ra s\u1ed1 ch\u00f3 l\u00e0:<\/p>\n

28 : 2 = 14 (con)<\/p>\n

S\u1ed1 g\u00e0 l\u00e0:<\/p>\n

36 \u2013 14 = 22 (con)<\/p>\n

Ghi ch\u00fa:<\/p>\n

C\u00f3 th\u1ec3 coi gi\u1ea3 thi\u1ebft t\u1ea1m \u1edf \u0111\u00e2y l\u00e0 t\u00ecnh hu\u1ed1ng \u201cM\u1ed7i con ch\u00f3 ch\u1ec9 c\u00f3 hai ch\u00e2n\u2026\u201d ho\u1eb7c b\u00e0i to\u00e1n \u0111\u01b0a ra l\u00e0: \u201cN\u1ebfu t\u1ea5t c\u1ea3 36 con ch\u00f3 \u0111\u1ec1u c\u00f3 2 ch\u00e2n…?\u201d.<\/p>\n

C\u00e1ch 2:<\/p>\n

Gi\u1ea3 s\u1eed ta g\u1eafn th\u00eam cho m\u1ed7i con g\u00e0 2 ch\u00e2n n\u1eefa (b\u1eb1ng b\u1ed9t) ch\u1eb3ng h\u1ea1n. Th\u1ebf th\u00ec m\u1ed7i con g\u00e0 \u0111\u1ec1u c\u00f3 4 ch\u00e2n v\u00e0 ta c\u00f3 th\u1ec3 coi c\u1ea3 36 con \u0111\u1ec1u l\u00e0 ch\u00f3 c\u1ea3.<\/p>\n

L\u00fac \u0111\u00f3 36 con ch\u00f3:<\/p>\n

36 x 4 = 144 (ch\u00e2n)<\/p>\n

S\u1ed1 ch\u00e2n g\u00e0 \u0111\u00e3 g\u1eafn th\u00eam l\u00e0:<\/p>\n

144 \u2013 100 = 44 (ch\u00e2n)<\/p>\n

S\u1ed1 g\u00e0 l\u00e0:<\/p>\n

44 : 2 = 22 (con)<\/p>\n

S\u1ed1 ch\u00f3 l\u00e0:<\/p>\n

36 \u2013 22 = 14 (con)<\/p>\n

Ghi ch\u00fa:<\/p>\n

C\u00f3 th\u1ec3 coi gi\u1ea3 thi\u1ebft t\u1ea1m \u1edf \u0111\u00e2y l\u00e0 t\u00ecnh hu\u1ed1ng \u201cM\u1ed7i con g\u00e0 \u0111\u1ec1u c\u00f3 4 ch\u00e2n\u2026\u201d ho\u1eb7c b\u00e0i to\u00e1n \u0111\u01b0a ra l\u00e0 \u201cN\u1ebfu 36 con \u0111\u1ec1u l\u00e0 ch\u00f3 c\u1ea3 th\u00ec c\u00f2n thi\u1ebfu bao nhi\u00eau c\u00e1i ch\u00e2n?\u201d.<\/p>\n

C\u00e1ch 3:<\/p>\n

Gi\u1ea3 s\u1eed ta \u201cch\u1eb7t b\u1edbt\u201d \u0111i m\u1ed9t n\u1eeda s\u1ed1 ch\u00e2n g\u00e0 v\u00e0 ch\u00f3. T\u1ee9c l\u00e0 m\u1ed7i con ch\u00f3 ch\u1ec9 c\u00f3 hai ch\u00e2n v\u00e0 m\u1ed7i con g\u00e0 ch\u1ec9 c\u00f3 1 ch\u00e2n. L\u00fac \u0111\u00f3 ta c\u00f3 b\u00e0i to\u00e1n:<\/p>\n

\u201cV\u1eeba g\u00e0 v\u1eeba ch\u00f3<\/p>\n

B\u00f3 l\u1ea1i cho tr\u00f2n<\/p>\n

Ba m\u01b0\u01a1i s\u00e1u con<\/p>\n

N\u0103m m\u01b0\u01a1i ch\u00e2n ch\u1eb5n\u201d.<\/p>\n

H\u1ecfi c\u00f3 bao nhi\u00eau con g\u00e0, bao nhi\u00eau con ch\u00f3?<\/p>\n

Trong b\u00e0i to\u00e1n tr\u00ean \u0111\u00e3 n\u00eau t\u1ea5t c\u1ea3 36 con \u0111\u1ec1u l\u00e0 g\u00e0 c\u1ea3 th\u00ec ta c\u00f3 36 ch\u00e2n. S\u1ed1 ch\u00e2n th\u1eeba ra l\u00e0:<\/p>\n

50 \u2013 36 = 14 (ch\u00e2n)<\/p>\n

M\u1ed7i con ch\u00f3 th\u1eeba ra m\u1ed9t ch\u00e2n m\u00e0 th\u1eeba ra t\u1ea5t c\u1ea3 14 ch\u00e2n. V\u1eady c\u00f3 14 con ch\u00f3<\/p>\n

Suy ra s\u1ed1 g\u00e0 l\u00e0:<\/p>\n

36 \u2013 14 = 22 (con)<\/p>\n

C\u00e1ch 4<\/p>\n

Gi\u1ea3 s\u1eed c\u00f3 18 con g\u00e0 v\u00e0 18 con ch\u00f3 (c\u00f3 th\u1ec3 gi\u1ea3 s\u1eed c\u00f3 \u201c20 con g\u00e0 v\u00e0 16 con ch\u00f3\u201d ho\u1eb7c 10 con g\u00e0 v\u00e0 26 con ch\u00f3\u201d… Mi\u1ec5n sao \u201ct\u1ed5ng s\u1ed1 g\u00e0 v\u00e0 ch\u00f3 b\u1eb1ng 36 con l\u00e0 \u0111\u01b0\u1ee3c\u201d).<\/p>\n

L\u00fac \u0111\u00f3 t\u1ed5ng s\u1ed1 ch\u00e2n g\u00e0 v\u00e0 ch\u00f3 s\u1ebd l\u00e0:<\/p>\n

18 x 2 + 18 x 4 = 108 (ch\u00e2n)<\/p>\n

Nh\u01b0ng th\u1ef1c t\u1ebf ch\u1ec9 c\u00f3 100 ch\u00e2n n\u00ean ph\u1ea3i t\u00ecm c\u00e1ch r\u00fat b\u1edbt \u0111i 8 ch\u00e2n m\u00e0 t\u1ed5ng s\u1ed1 con v\u1eabn kh\u00f4ng thay \u0111\u1ed5i.<\/p>\n

Ta th\u1ea5y: n\u1ebfu thay 1 con ch\u00f3 b\u1eb1ng 1 con g\u00e0 th\u00ec t\u1ed5ng s\u1ed1 con v\u1eabn kh\u00f4ng thay \u0111\u1ed5i nh\u01b0ng t\u1ed5ng s\u1ed1 ch\u00e2n s\u1ebd gi\u1ea3m \u0111i:<\/p>\n

4 \u2013 2 = 2 (ch\u00e2n)<\/p>\n

V\u1eady mu\u1ed1n cho t\u1ed5ng s\u1ed1 ch\u00e2n gi\u1ea3m \u0111i 8 th\u00ec s\u1ed1 con ch\u00f3 ph\u1ea3i thay b\u1eb1ng g\u00e0 l\u00e0:<\/p>\n

8 : 2 = 4 (con)<\/p>\n

Do \u0111\u00f3 s\u1ed1 g\u00e0 l\u00e0:<\/p>\n

18 + 4 = 22 (con )<\/p>\n

S\u1ed1 ch\u00f3 l\u00e0:<\/p>\n

36 \u2013 22 = 14 (con)<\/p>\n

\u0110\u00e1p s\u1ed1: 22 con g\u00e0<\/p>\n

14 con ch\u00f3.<\/p>\n","protected":false},"excerpt":{"rendered":"

C\u00c2U 1: \u0110i\u1ec1n ti\u1ebfp v\u00e0o d\u1ea5u (?). C\u00c2U 2: \u0110i\u1ec1n ti\u1ebfp v\u00e0o d\u1ea5u (?). C\u00c2U 3: T\u1eeb m\u1ed9t t\u1edd gi\u1ea5y k\u1ebb \u00f4 vu\u00f4ng, b\u1ea1n khang c\u1eaft ra m\u1ed9t h\u00ecnh sao b\u1ed1n c\u00e1nh nh\u01b0 h\u00ecnh d\u01b0\u1edbi. H\u1ecfi h\u00ecnh sao n\u00e0y c\u00f3 di\u1ec7n T\u00edch b\u1eb1ng m\u1ea5y \u00f4 vu\u00f4ng? C\u00c2U 4: Nh\u00e0 kia c\u00f3 hai v\u1ee3 ch\u1ed3ng, 6 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[47],"tags":[],"class_list":["post-25443","post","type-post","status-publish","format-standard","hentry","category-do-vui"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/25443","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=25443"}],"version-history":[{"count":1,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/25443\/revisions"}],"predecessor-version":[{"id":25453,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/25443\/revisions\/25453"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=25443"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=25443"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=25443"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}