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标题: 请教一条数学题~~谢谢 [打印本页]

作者: honeypony 时间: 2011-5-8 09:52 标题: 请教一条数学题~~谢谢

If x and y are nonzero integers, is 18 a factor of xy2?
(1)x is a multiple of 54.
(2)y is a multiple of 6.

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.
Answer: D

为什么不是选c呢？~~求解答~~谢谢~~

作者: 小宇宙2010 时间: 2011-5-8 20:09

c是单独不行，合起来可以。
d是不用合，单独就可以。

所以：D

作者: teddyabc 时间: 2011-5-11 20:56

(1)x is a multiple of 54， then x is surely a multiple of 18, so 1 alone is sufficient.

(2)y is a multiple of 6, then y^2 is a multiple of 36 as well as a mutiple of 18, so 2 alone is suffcient

Based on the two, we choose D. EACH statement ALONE is sufficient

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