What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?
Pick.
A) 196 B) 630 C) 680 D) 780 E) 960
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: Option 630
<result>B</result>
What will be the least number which when doubled will be exactly divisible by 12, 18, 21 and 30 ?