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 = 22 * 32 * 5.
To make it a perfect square, it must be multiplied by 5.
Required number = (22 * 32 * 52) = 900.