jhudson wrote:
If 60xn is the square of an integer, what is the least possible value that n could have?
a: 6
b: 9
c: 12
D: 15
E: 60
a: 6
b: 9
c: 12
D: 15
E: 60
Recall that squares of integers have even powers of primes i.e. 9 = 3^2, 16 = 2^4, 36 = 2^2*3^2 etc
60 = 2^2*3*5
Notice that to make a perfect square, we need at least a 3 and a 5.
60n = 2^2*3^2*5^2 (all even powers)
So n must be at least 3*5 = 15