ratio 計算

treewing929 · 发表于 2012-3-1 15:28:44

A certain club has 20 members.What is the ratio of the member of 5-member committees that can be formed from the members of the club to the number of 4-member committees that can be formed from the members of the club?

A.16 to 1

B.15 to 1

C.16 to 5

D.15 to 6

E.5 to 4

這條問題如何理解? 為什麼是 16 to 5??求解. 謝!!

瓜娃子 · 发表于 2012-3-1 15:34:20

瓜娃子 · 发表于 2012-3-1 15:34:55

http://gmatclub.com/forum/permutaion-combination-77015.html
里面二楼解答～

treewing929 · 发表于 2012-3-1 15:35:18

For a nonnegative integer n, if the remainder is 1 when 2n is divided by 3, then which of the following must be true?

I. n is greater than zero.

這個選項是不對. 請問這個選項有沒有數式可以證明 not true? 還是只有代數?

瓜娃子 · 发表于 2012-3-1 15:43:35

确实没看出来为什么not true....麻烦lz讲解....

treewing929 · 发表于 2012-3-1 15:48:22

确实没看出来为什么not true....麻烦lz讲解....

-- by 会员瓜娃子 (2012/3/1 15:43:35)

For a nonnegative integer n, if the remainder is 1 when 2ⁿ is divided by 3, then which of the following must be true?

I.n is greater than zero.

II.3ⁿ = (-3)ⁿ

III.√2ⁿis an integer.

A.I only
B.II only

C.I and II
D.I and III
E.II and III

這是題目. 答案是 e. 我也不大肯定所以在這裡問問大家. 哈

多謝你上一條的幫忙!! 感謝!

treewing929 · 发表于 2012-3-1 15:50:31

我是代n=0, 所以也有餘數 1
有沒有數式?

瓜娃子 · 发表于 2012-3-1 15:51:04

好吧....原来问题出在2n上...怪不得一次没看懂.....

treewing929 · 发表于 2012-3-1 15:56:20

這條我是想到 pattern: n = 2,4,6...even intergers 才可以有餘數一
不知道有沒有其他數式思路幫助呢?

瓜娃子 · 发表于 2012-3-1 15:57:05

不知道额..貌似代数最简单吧...画图可以么...不过都没有代数简单吧...

ratio 計算

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