Question

Find the least square number which is exactly divisible by each of the numbers 6, 9, 15 and 20.

Answer 1

The smallest number divisible by each of these numbers is their L.C.M.
L.C.M. of 6, 9, 15, 20 = 180

Resolving into prime factors:
$180=2\times 2\times 3\times 3\times 5$
To make it a perfect square, we multiply it with 5.

Required number = $180\times 5=900$