GMAT Problem Solving (PS) | Re: The function f(x) is defined for all positive integers x as

SOLUTION

The function f(x) is defined for all positive integers x as the number of even factors of x and the function g(x) is defined for all positive integers x as the number of odd factors of x. For positive integers a and b if f(b)*g(a) = 0 and f(a) = 1, which of the following could be the least common multiple of a and b?

A. 12
B. 16
C. 20
D. 30
E. 36

f(b)*g(a) = 0 any positive integer has at least one odd factor: 1. Thus, g(a) cannot be 0, which implies that f(b) = 0. This
...

---