{"id":25436,"date":"2021-12-24T16:43:58","date_gmt":"2021-12-24T09:43:58","guid":{"rendered":"https:\/\/www.vietlearn.org\/post\/?p=25436"},"modified":"2021-12-24T16:44:26","modified_gmt":"2021-12-24T09:44:26","slug":"bai-so-2-do-vui-luyen-tri-thong-minh","status":"publish","type":"post","link":"https:\/\/www.vietlearn.org\/kien-thuc\/bai-so-2-do-vui-luyen-tri-thong-minh\/","title":{"rendered":"B\u00c0I S\u1ed0 2 – \u0110\u1ed1 vui luy\u1ec7n tr\u00ed th\u00f4ng minh"},"content":{"rendered":"

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

H\u00ecnh n\u00e0o h\u1ee3p l\u00fd nh\u1ea5t?<\/p>\n

<\/a>\"7.jpg\"C\u00c2U 2:<\/h3>\n

M\u1ed9t b\u1ea1n ch\u1ecdn hai s\u1ed1 t\u1ef1 nhi\u00ean tu\u1ef3 \u00fd, T\u00ednh t\u1ed5ng c\u1ee7a ch\u00fang r\u1ed3i l\u1ea5y t\u1ed5ng \u0111\u00f3 nh\u00e2n v\u1edbi ch\u00ednh n\u00f3. B\u1ea1n \u1ea5y c\u0169ng l\u00e0m t\u01b0\u01a1ng t\u1ef1 \u0111\u1ed1i v\u1edbi hi\u1ec7u c\u1ee7a hai s\u1ed1 m\u00e0 m\u00ecnh \u0111\u00e3 ch\u1ecdn \u0111\u00f3. Cu\u1ed1i c\u00f9ng c\u1ed9ng hai T\u00edch t\u00ecm \u0111\u01b0\u1ee3c v\u1edbi nhau. H\u1ecfi r\u1eb1ng t\u1ed5ng c\u1ee7a hai T\u00edch \u0111\u00f3 l\u00e0 s\u1ed1 ch\u1eb5n hay s\u1ed1 l\u1ebb? V\u00ec sao?<\/p>\n

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

B\u00e0i to\u00e1n c\u1ed5:<\/p>\n

Tr\u0103m tr\u00e2u, tr\u0103m c\u1ecf<\/p>\n

Tr\u00e2u \u0111\u1ee9ng \u0103n n\u0103m<\/p>\n

Tr\u00e2u n\u1eb1m \u0103n ba<\/p>\n

L\u1ee5 kh\u1ee5 tr\u00e2u gi\u00e0<\/p>\n

Ba con m\u1ed9t b\u00f3.<\/p>\n

H\u1ecfi c\u00f3 bao nhi\u00eau con tr\u00e2u \u0111\u1ee9ng, tr\u00e2u n\u1eb1m, tr\u00e2u gi\u00e0?<\/p>\n

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

M\u1ed9t s\u1ee3i d\u00e2y 3m c\u1ed9t con ng\u1ef1a c\u00e1ch \u0111\u1ed1ng c\u1ecf 8m nh\u01b0ng con ng\u1ef1a v\u1eabn \u0103n c\u1ecf \u1edf \u0111\u00f3 \u0111\u01b0\u1ee3c nh\u01b0 th\u01b0\u1eddng, kh\u00f4ng c\u00f3 ai gi\u00fap. H\u1ecfi t\u1ea1i sao?<\/p>\n

\"8_1.jpg\"<\/p>\n

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

<\/a>B\u00c0I S\u1ed0 2<\/h2>\n

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

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

H\u00ecnh b.<\/p>\n

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

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

S\u1ebd x\u1ea3y ra m\u1ed9t trong hai tr\u01b0\u1eddng h\u1ee3p: C\u1ea3 hai s\u1ed1 \u0111\u1ec1u ch\u1eb5n (ho\u1eb7c \u0111\u1ec1u l\u1ebb); m\u1ed9t s\u1ed1 ch\u1eb5n v\u00e0 m\u1ed9t s\u1ed1 l\u1ebb.<\/p>\n

a. Hai s\u1ed1 ch\u1eb5n (ho\u1eb7c hai s\u1ed1 l\u1ebb). T\u1ed5ng, hi\u1ec7u c\u1ee7a hai s\u1ed1 \u0111\u00f3 l\u00e0 s\u1ed1 ch\u1eb5n. S\u1ed1 ch\u1eb5n nh\u00e2n v\u1edbi ch\u00ednh n\u00f3 \u0111\u01b0\u1ee3c s\u1ed1 ch\u1eb5n. Do \u0111\u00f3 c\u1ed9ng hai t\u00edch (l\u00e0 hai s\u1ed1 ch\u1eb5n) ph\u1ea3i \u0111\u01b0\u1ee3c s\u1ed1 ch\u1eb5n.<\/p>\n

b. M\u1ed9t s\u1ed1 ch\u1eb5n v\u00e0 m\u1ed9t s\u1ed1 l\u1ebb. T\u1ed5ng, hi\u1ec7u c\u1ee7a ch\u00fang \u0111\u1ec1u l\u00e0 s\u1ed1 l\u1ebb. S\u1ed1 l\u1ebb nh\u00e2n v\u1edbi ch\u00ednh n\u00f3 \u0111\u01b0\u1ee3c s\u1ed1 l\u1ebb. Do \u0111\u00f3 c\u1ed9ng hai t\u00edch (l\u00e0 hai s\u1ed1 l\u1ebb) ph\u1ea3i \u0111\u01b0\u1ee3c s\u1ed1 ch\u1eb5n.<\/p>\n

V\u1eady theo \u0111i\u1ec1u ki\u1ec7n \u0111\u00e3 cho th\u00ec k\u1ebft qu\u1ea3 c\u1ee7a b\u00e0i to\u00e1n ph\u1ea3i l\u00e0 s\u1ed1 ch\u1eb5n.<\/p>\n

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

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

Gi\u1ea3 s\u1eed s\u1ed1 b\u00f3 c\u1ecf m\u00e0 m\u1ed7i lo\u1ea1i tr\u00e2u \u0103n \u0111\u1ec1u t\u0103ng l\u00ean g\u1ea5p ba.<\/p>\n

Th\u1ebf th\u00ec ta c\u00f3 b\u00e0i to\u00e1n: \u201cC\u00f3 100 con tr\u00e2u v\u00e0 300 b\u00f3 c\u1ecf. M\u1ed7i con tr\u00e2u \u0111\u1ee9ng \u0103n 15 b\u00f3 (5 x 3 = 15), m\u1ed7i con tr\u00e2u n\u1eb1m \u0103n 9 b\u00f3 (3 x 3 = 9), m\u1ed7i con tr\u00e2u gi\u00e0 \u0103n 1 b\u00f3. H\u1ecfi c\u00f3 bao nhi\u00eau tr\u00e2u \u0111\u1ee9ng, tr\u00e2u n\u1eb1m, tr\u00e2u gi\u00e0?\u201d.<\/p>\n

Ta k\u00ed hi\u1ec7u s\u1ed1 tr\u00e2u \u0111\u1ee9ng l\u00e0 \u0111, s\u1ed1 tr\u00e2u n\u1eb1m l\u00e0 N, s\u1ed1 tr\u00e2u gi\u00e0 l\u00e0 g. Th\u1ebf th\u00ec t\u1ed5ng s\u1ed1 b\u00f3 c\u1ecf m\u00e0 m\u1ed7i lo\u1ea1i tr\u00e2u \u0103n l\u00e0:<\/p>\n

\"93.jpg\"<\/p>\n

Tr\u00e2u \u0111\u1ee9ng<\/p>\n

Tr\u00e2u n\u1eb1m<\/p>\n

Tr\u00e2u gi\u00e0<\/p>\n

100 con tr\u00e2u 300 b\u00f3 c\u1ecf<\/p>\n

Nh\u00ecn v\u00e0o s\u01a1 \u0111\u1ed3 ta th\u1ea5y:<\/p>\n

\u0110 x 15 + N x 9 + g = 300 (b\u00f3 c\u1ecf)<\/p>\n

V\u1eady ta c\u00f3:<\/p>\n

\u0110 x 14 + N x 8 = 300 \u2013 100 = 200<\/p>\n

Chia \u0111\u00f4i ta \u0111\u01b0\u1ee3c:<\/p>\n

\u0110 x 7 + N x 4 = 100 (1)<\/p>\n

\u0110 x 3 + \u0110 x 4 + N x 4 = 25 x 4<\/p>\n

\u0110 x 3 = 25 x 4 \u2013 \u0110 x 4 \u2013 N x 4<\/p>\n

\u0110 x 3 = (25 \u2013 \u0110 \u2013 N) x 4<\/p>\n

Suy ra (\u0110 x 3) chia h\u1ebft cho 4 do \u0111\u00f3 \u0110 chia h\u1ebft cho 4.<\/p>\n

M\u1eb7t kh\u00e1c t\u1eeb (1) ta c\u00f3: \u0110 x 7 < 100 \u2013 4 = 96<\/p>\n

V\u1eady \u0110 < 14, m\u1eb7t kh\u00e1c \u0110 chia h\u1ebft cho 4, n\u00ean \u0110 ch\u1ec9 c\u00f3 th\u1ec3 l\u00e0 4, 8 v\u00e0 12. Ta l\u1ea7n l\u01b0\u1ee3t th\u1eed \u0111\u1ed1i v\u1edbi t\u1eebng gi\u00e1 tr\u1ecb c\u1ee7a \u0110 \u0111\u1ec3 t\u00ecm c\u00e1c gi\u00e1 tr\u1ecb t\u01b0\u01a1ng \u1ee9ng c\u1ee7a N v\u00e0 G, v\u00e0 ghi k\u1ebft qu\u1ea3 v\u00e0o b\u1ea3ng sau:<\/p>\n\n\n\n\n\n\n\n
Tr\u00e2u \u0111\u1ee9ng<\/td>\nTr\u00e2u n\u1eb1m<\/td>\nTr\u00e2u gi\u00e0<\/td>\n<\/tr>\n
S\u1ed1 con<\/td>\nS\u1ed1 c\u1ecf<\/td>\nS\u1ed1 con<\/td>\nS\u1ed1 c\u1ecf<\/td>\nS\u1ed1 con<\/td>\nS\u1ed1 c\u1ecf<\/td>\n<\/tr>\n
4<\/td>\n20<\/td>\n18<\/td>\n54<\/td>\n78<\/td>\n26<\/td>\n<\/tr>\n
8<\/td>\n40<\/td>\n11<\/td>\n33<\/td>\n81<\/td>\n27<\/td>\n<\/tr>\n
12<\/td>\n60<\/td>\n4<\/td>\n12<\/td>\n84<\/td>\n28<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n

(Trong khi t\u00ednh to\u00e1n, ta t\u00ednh s\u1ed1 b\u00f3 c\u1ecf m\u1ed7i lo\u1ea1i tr\u00e2u \u0103n theo \u0111\u1ea7u b\u00e0i g\u1ed1c: tr\u00e2u \u0111\u1ee9ng \u0103n n\u0103m, tr\u00e2u n\u1eb1m \u0103n ba, tr\u00e2u gi\u00e0 3 con 1 b\u00f3).<\/p>\n

V\u1eady b\u00e0i to\u00e1n c\u00f3 3 \u0111\u00e1p s\u1ed1: s\u1ed1 tr\u00e2u \u0111\u1ee9ng, tr\u00e2u n\u1eb1m, tr\u00e2u gi\u00e0 l\u1ea7n l\u01b0\u1ee3t l\u00e0:<\/p>\n

(4, 18, 78); ho\u1eb7c (8, 11, 81); ho\u1eb7c (12, 4, 84).<\/p>\n

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

Khi gi\u1ea3i b\u00e0i to\u00e1n tr\u00ean ta \u0111\u00e3 xem x\u00e9t t\u1ea5t c\u1ea3 c\u00e1c tr\u01b0\u1eddng h\u1ee3p c\u00f3 th\u1ec3 x\u1ea3y ra trong b\u00e0i, r\u1ed3i l\u1ea7n l\u01b0\u1ee3t ki\u1ec3m tra xem tr\u01b0\u1eddng h\u1ee3p n\u00e0o b\u1ecb lo\u1ea1i, tr\u01b0\u1eddng h\u1ee3p n\u00e0o ch\u1ea5p nh\u1eadn \u0111\u01b0\u1ee3c. C\u00e1ch gi\u1ea3i nh\u01b0 v\u1eady g\u1ecdi l\u00e0 gi\u1ea3i theo ph\u01b0\u01a1ng ph\u00e1p l\u1ef1a ch\u1ecdn.<\/p>\n

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

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

V\u00ec s\u1ee3i d\u00e2y ch\u1ec9 c\u1ed9t v\u00e0o c\u1ed5 con ng\u1ef1a m\u1ed9t \u0111\u1ea7u, nh\u01b0ng \u0111\u1ea7u s\u1ee3i d\u00e2y kia l\u1ea1i kh\u00f4ng bu\u1ed9c v\u00e0o c\u1ecdc n\u00ean con ng\u1ef1a c\u00f3 th\u1ec3 t\u1ef1 do \u0103n \u0111\u1ed1ng c\u1ecf.<\/p>\n","protected":false},"excerpt":{"rendered":"

C\u00c2U 1: H\u00ecnh n\u00e0o h\u1ee3p l\u00fd nh\u1ea5t? C\u00c2U 2: M\u1ed9t b\u1ea1n ch\u1ecdn hai s\u1ed1 t\u1ef1 nhi\u00ean tu\u1ef3 \u00fd, T\u00ednh t\u1ed5ng c\u1ee7a ch\u00fang r\u1ed3i l\u1ea5y t\u1ed5ng \u0111\u00f3 nh\u00e2n v\u1edbi ch\u00ednh n\u00f3. B\u1ea1n \u1ea5y c\u0169ng l\u00e0m t\u01b0\u01a1ng t\u1ef1 \u0111\u1ed1i v\u1edbi hi\u1ec7u c\u1ee7a hai s\u1ed1 m\u00e0 m\u00ecnh \u0111\u00e3 ch\u1ecdn \u0111\u00f3. Cu\u1ed1i c\u00f9ng c\u1ed9ng hai T\u00edch t\u00ecm \u0111\u01b0\u1ee3c v\u1edbi […]<\/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-25436","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\/25436","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=25436"}],"version-history":[{"count":3,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/25436\/revisions"}],"predecessor-version":[{"id":25442,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/25436\/revisions\/25442"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=25436"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=25436"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=25436"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}