Find the least number that is divisible by 12, 18, 21, and 30.

Correct option is B

Solution:

To find the least number divisible by all the given numbers, we need to calculate their Least Common Multiple (LCM).

Prime factorization of the given numbers:

​$$12 = 2^2 \times 3 \\18 = 2 \times 3^2 \\21 = 3 \times 7 \\30 = 2 \times 3 \times 5$$

The LCM is found by taking the highest powers of all prime factors present in the factorizations:

​$$LCM = 2^2 \times 3^2 \times 5 \times 7 \\LCM = 4 \times 9 \times 5 \times 7 \\LCM = 1260$$​​

​Therefore, the least number that is divisible by 12, 18, 21, and 30 is 1260​