1.  What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?

A. 196
B. 630
C. 1260
D. 2520

Answer: Option B

Explanation:

L.C.M. of 12, 18, 21 30

= 2 x 3 x 2 x 3 x 7 x 5

= 1260.

Required number = (1260 ÷2) = 630.