还有一道数学关于integer的，求救大牛-GWD

ybava018919

If n is the product of the integers from1 to 20 inclusive, what is the greatest integer k for which 2^k is a factor of n?


A.10
B.12
C.15
D.18
E.20
Answer:  D
But I don't know how to start it，I've forgot the content for long time. One more, are there any strategy to do this kind of question?  Than--an--an---anks

stevezzy

here is the link to that question from beatthegmat website which is also an excellen website for gmat prep:

http://www.beatthegmat.com/ps-confused-about-factorials-and-factors-t21955.html

mecsid

数数1到20的乘积里面有几个2就好了  2一个 4两个 6一个 8三个。。。以此类推  加起来就是18

ybava018919

还是不是很明白，什么叫数数1到20的乘积里有几个2？？比较愚笨O(∩_∩)O~~

mecsid

题目是2^k次方是1－20乘积的一个因子 问最大的k的值   1－20的乘积就是1＊2＊3＊。。。。。＊20咯  你只要找出每个数本身带了几个2 不就知道整个乘积的因子可以是2的几次方了么？  。。。。我表达能力可能有问题。。。。

ybava018919

谢谢谢谢谢~~~~~~~~~~~~~明白了~~~~~~~~~

ybava018919

here is the link to that question from beatthegmat website which is also an excellen website for gmat prep:

http://www.beatthegmat.com/ps-confused-about-factorials-and-factors-t21955.html

-- by 会员 stevezzy (2010/6/28 12:07:52)

万谢~