求PREP难题~~~！！！

duluxstar

问： n, y are both positive integers, if 450y=n^3, which of the following must be an integer?

I. Y/3x2^2x5

II. Y/3^2x2x5

III. Y/3x2x5^2

A. None
B. I only
C. II only
D III only
E. I, II, and III

Answer: B.

怎样才能比较快地solve这道题呢？ 谢谢指点！！！

智者多能

450=5^2x3^2x2, 如果450y=n^3,那么Y至少要满足以y=5x3x2^2, 这样才能满足原来等式

duluxstar

many  thanks .