请教GWD-1-Q15

bipedalism · 发表于 2007-10-10 19:06:00

If p is the product of the integers from 1 to 30, inclusive, what is the greatest integer k for which 3^k is a factor of p?

A. 10

B. 12

C. 14

D. 16

E. 18

答案是C，请教思路

Elynn_Chen · 发表于 2007-10-10 19:14:00

list them, see.

3, 6, 9, 12, 15, 18, 21, 24, 27, 30

3, 3*2, 3^2, 3*4, 3*5, 3^2*2, 3*7, 3*8, 3^3, 3*10

1 + 1 + 2 + 1 + 1 + 2 + 1 + 1 + 3 + 1= 14 (this means how many 3 there are in the product of 1-30)

[此贴子已经被作者于2007-10-10 19:14:49编辑过]

bipedalism · 发表于 2007-10-11 15:27:00

啊,明白了明白了，题目问得有够绕。多谢MM

emilzhu750 · 发表于 2007-10-11 22:52:00

什么意思啊这道题目看不懂啊：（

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