What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?  Pick
A) 1260	B) 630	C) 2524	D) 1680	E) 2250
L.C.M. of 12, 18, 21 30 2 | 12 - 18 - 21 - 30   ----------------------------   = 2 x 3 x 2 x 3 x 7 x 5 = 1260. 3 | 6 - 9 - 21 - 15   ----------------------------   Required number = (1260 ÷ 2) | 2 - 3 - 7 - 5   = 630. ANSWER : 630
<result>B</result>
What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?