Question:
Find the least square number which is exactly divisible by each of the numbers 6, 9, 15 and 20.
Solution:
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 $=180 \times 5=900$