gmat数学题

题目

gmat数学题
Q15:
If n is a positive integer and r is the remainder when (n – 1)(n + 1) is divided by 24,what is the value of
(1)x05 2 is not a factor of n.
(2)x05 3 is not a factor of n.
x05x05
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

选C
你把那些既不是3的倍数也不是2的倍数的数(如5,7,11,13)带进去发现,都是24的倍数.
但是把几个是3的倍数而不是2的倍数的数,和是2的而不是3的倍数的数带进去,发现余数有很多种,无法确定.