meparashar wrote:
Does the integer k have at least three different positive prime factors?
1) k/15 is an integer
2) k/10 is an integer
We need to determine whether k has at least three different prime factors.
Statement One Alone:
k/15 is an integer.
Statement one alone is not sufficient to answer the question. If k = 15, then k has two different prime factors; however, if k = 30, then k has three different prime factors.
Statement Two Alone:
k/10 is an integer.
Statement two alone is not sufficient to answer the question. If k = 10, then k has two different prime factors; however, if k = 30, then k has three different prime factors.
Statements One and Two Together:
Using statements one and two, we see that k is a multiple of both 10 and 15, and thus it is a multiple of their least common multiple, which is 30. Since all multiples of 30 have at least three different prime factors, the two statements together are sufficient.
Answer:
C