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教育王國 › 討論區 › 小學雜談 › math question for help

查看: 734\|回覆: 9	go math question for help [複製鏈接]

chauch

民房

Rank: 1


	10

1^#

發表於 08-12-23 11:43 |只看該作者 |倒序瀏覽 |打印

Can anybody help?

A pack of biscuits to be shared equally among
3 children --> 2 biscuits left
5 children --> 3 biscuits left
7 children --> 4 biscuits left

What is the minimum number of biscuits in that pack of biscuits

0 0 0 0

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baekdoosan

大宅

Rank: 5 Rank: 5


	1889

2^#

發表於 08-12-23 11:54 |只看該作者

answer: 53

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chauch

民房

Rank: 1


	10

3^#

發表於 08-12-23 11:57 |只看該作者

回覆 # 的文章

Thank you.
Can you show us the steps in reaching the answer.

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baekdoosan

大宅

Rank: 5 Rank: 5


	1889

4^#

發表於 08-12-23 14:44 |只看該作者

N = 2(mod3)
N = 3(mod5)
N = 4(mod7)

5x7 = 35 is the smallest no. which is divisible by 5 and 7 and has remainder of 2 when divided by 3

3x7 = 21 is the smallest no. which is divisible by 3 and 7 and has a remainder of 1 when divided by 5
therefore 21x3 = 63 is divisible by 3 and 7 and has a remainder of 3 when divided by 5

3x5 = 15 is the smallest no. which is divisible by 3 and 5 and has a remainder of 1 when divided by 7
therefore 15x4 = 60 is divisible by 3 and 5 and has a remainder of 4 when divided by 7

LCM 3x5x7 = 105

N = 35+63+60 + 105t where t is integer
N = 158 + 105t (general solution)
N = 53 is smallest when (t = -1)

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chauch

民房

Rank: 1


	10

5^#

發表於 08-12-23 15:39 |只看該作者

回覆 # 的文章

Thanks very much.

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mandy_lee

大宅

Rank: 5 Rank: 5


	3060

6^#

發表於 08-12-24 11:41 |只看該作者

原帖由 chauch 於 08-12-23 15:39 發表
Thanks very much.

幾年班maths 題目

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chauch

民房

Rank: 1


	10

7^#

發表於 08-12-24 13:23 |只看該作者

回覆 # 的文章

It's just an I.Q. math question for a P 5 student. We can get to the answer by simple logical thinking (trial by error), but the approach posted by baekdoosan is obviously beyond primary or even secondary school level.

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Heidibaba

複式洋房

Rank: 3 Rank: 3


	218

8^#

發表於 08-12-25 00:02 |只看該作者

三人同行七十稀
五樹梅花廿一枝
七子團圓正半月
餘百零五便得知

三三數之，餘數乘以七十
五五數之，餘數乘以廿一
七七數之，餘數乘以十五
三者相加，如不大於一百零五，即為答案；否則須減去一百零五或其倍數

(金庸．射鵰英雄傳)

原帖由 chauch 於 08-12-23 11:43 發表
Can anybody help?

A pack of biscuits to be shared equally among
3 children --> 2 biscuits left
5 children --> 3 biscuits left
7 children --> 4 biscuits left

What is the minimum number of biscuits i ...