**Find the least square number which is exactly divisible by 10,12,15 and 18.**

999

900

899

987

B. 900

L.C.M. of 10, 12, 15, 18 = 180. Now, 180 = 2 * 2 * 3 * 3 *5 = 2^{2} * 3^{2 }* 5.

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

Required number = (2^{2} * 3^{2} * 5^{2}) = 900.