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

Question: What is the least number which, when doubled, will be exactly divisible by 12, 18, 21, and 30?Solution: Let, the least number be xThen, 2x must be divisible by 12, 18, 21, and 30.∴ 2x = LCM(12,18,21,30)L.C.M. of 12, 18, 21, 30 = 2 × 2 × 3 × 3 × 7 × 5= 1260∴ Required number = 1260/2 = 630