GWD MATH 19,29

shevit · 发表于 2011-6-10 01:34:09

Q29:
Is the integer n odd?
(1)n is divisible by 3.
(2)2n is divisible by twice as many positive integers as n.

A. Statement (1) ALONE is sufficient, but statement (2) alone is not sufficient.
B. Statement (2) ALONE is sufficient, but statement (1) alone is not sufficient.
C. BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient.
D. EACH statement ALONE is sufficient.
E. Statements (1) and (2) TOGETHER are NOT sufficient.
答案是B

Rainbeauty · 发表于 2011-6-10 14:17:12

对于2，一个办法可以带数字，另一个办法可以通过一般性分析
若n为奇数，n=2k+1 (约数：1,2k+1),2n=4k+2(约数：1,2,2k+1,4K+2)
若n为偶数，n=2k (约数：1,2,k,2k),2n=4k(约数：1,2,k,2k,4,4k)
通过以上分析发现，2n的约数为n的2倍，就说明n为奇数。
所以B

GWD MATH 19,29

所属分类: GMAT考试

正在浏览此版块的会员 ()