LCM for 3 and 21

The first method to find LCM for numbers 3 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:

LCM = (Number1 × Number2) ÷ GCF

GCF of numbers 3 and 21 is 3, so

LCM = (3 × 21) ÷ 3

LCM = 63 ÷ 3

LCM = 21

The second method to find LCM for numbers 3 and 21 is to list out the common multiples for both nubmers and pick the first which matching:

Multiples of 3: 3, 6, 9, 12, 15, 18, 21, 24, 27

Multiples of 21: 21, 42, 63, 84, 105, 126, 147, 168, 189, [...], 21

So the LCM for 3 and 21 is 21

Another method to find LCM for numbers 3 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors: