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

We know that,

The smallest number that is divisible by each o0f these numbers is their L.C.M


So,


L.C.M of 6, 9, 15, 20 = 180


Resolving into prime factors, we get


180 = 2 × 2 × 3 × 3 × 5


So, for making it a perfect square we have to multiply it by 5


Multiplying the number by 5, we get


Required number = 180 × 5


= 900


17