# How many factors of 1080 are perfect squares?

 [ A ]    4 [ B ]    6 [ C ]    8 [ D ]    5
 Answer : Option D Explanation : 1080 = $2 3$ $\times$ $3 3$ $\times$ 5. For any perfect square, all the powers of the primes have to be even numbers. So, if the factor is of the form $2^ a$ $\times$ $3^ b$ $\times$$5^ c$ . The values 'a' can take are 0 and 2, b can take are 0 and 2, and c can take the value 0. Totally there are 4 possibilities. 1, 4, 9, and 36.