Find the least square number which is divisible by 10, 12, 15 and 18?

L.C.M of 10, 12,15, 18

Answer will be 180.

Factors of 180 are: 2*2*3*3*5

or 

2² * 3³ *5

To make it a perfect square, it must be multiplied by 5.

Required number:

= 2² * 3² *5²

= 900 (Answer)