Now that you’ve gotten a little more confident, we’re going to give you the opportunity to practice "without the training wheels." When you want to check your work, you can turn to the solutions at the end. If you aren’t familiar with some of the mathematical concepts, make a note to pay particular attention to that chapter in this book; this practice set covers a wide range of topics tested on the GMAT.
On all data sufficiency problems, the answer choices are the same (as you’ve learned). We’ve put them here for your reference.
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.
How many prime factors of x are also prime factors of y
(1) x=30
(2) y is a multiple of x.
参考答案：C
解析：Statement (1) tells us nothing about the prime factors of y, so it is not sufficient on its own. We can eliminate A and D. We do know at this point, though, that the set of prime factors in question is {2, 3, 5}.
Statement (2) on its own tells us nothing about the prime factors of x, so it is not sufficient on its own. We can eliminate B.
Putting them together, we can see that all of the prime factors of x would also be prime factors of y, so they have those same three prime factors in common. Since the statements are sufficient together, then answer is C.