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

Question: 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 | 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.