# What is the LCM of 3 and 21

To find the LCM of 3 and 21, we need the least number which is exactly divisible by both 3 and 21.

## Answer: LCM of 3 and 21 is 21

The two methods that are used to find the LCM (Least Common Multiple) of 3 and 21 are given below.

**Explanation:**

The two methods that we are using to find LCM(3, 21) are.

- LCM of 3 and 21 by Formula
- LCM of 3 and 21 by Listing Method

### Method1: LCM of 3 and 21 by Formula

The formula of LCM is LCM (a,b) = (a × b) / GCF (a,b)

The Greatest Common Factor (GCF) of (3, 21) = 3

By formula,

LCM (3, 21) = (3 × 21) / GCF (3, 21)

= (3 × 21) / 3

= 21

So, LCM of 3 and 21 = 21

### Method2: LCM of 3 and 21 by Listing Method

Let's see the first few multiples of 3 and 21 and identify the common multiples of 3 and 21.

The least among the common multiples is the LCM of 3 and 21

Clearly, 21 is the least common multiple of 3 and 21

So, irrespective of the method, the solution to our question LCM of 3 and 21 is the same.