LCM for 15 and 21
What's the Least Common Multiple (LCM) of 15 and 21?
(One hundred five)
Finding LCM for 15 and 21 using GCF's of these numbers
The first method to find LCM for numbers 15 and 21 is to find Greatest Common Factor (GCF) of these numbers. Here's the formula:
LCM = (Number1 × Number2) ÷ GCF
GCF of numbers 15 and 21 is 3, so
LCM = (15 × 21) ÷ 3
LCM = 315 ÷ 3
LCM = 105
Finding LCM for 15 and 21 by Listing Multiples
The second method to find LCM for numbers 15 and 21 is to list out the common multiples for both nubmers and pick the first which matching:
Multiples of 15: 15, 30, 45, 60, 75, 90, 105, 120, 135
Multiples of 21: 21, 42, 63, 84, 105, 126, 147
So the LCM for 15 and 21 is 105
Finding LCM for 15 and 21 by Prime Factorization
Another method to find LCM for numbers 15 and 21 is to list all Prime Factors for both numbers and multiply the highest exponent prime factors:
All Prime Factors of 15: 3, 5 (exponent form: 31, 51)
All Prime Factors of 21: 3, 7 (exponent form: 31, 71)
31 × 51 × 71 = 105
Related Calculations
See Also
- Greatest Common Factor - Find the Greatest Common Factor (GCF) of two numbers
<a href="https://calculat.io/en/number/least-common-multiple-lcm-of/15--21">What is the LCM of 15 and 21? - Calculatio</a>
LCM Table
About "Least Common Multiple" Calculator
Least Common Multiple (LCM) also known as the Lowest Common Multiple or Smallest Common Multiple of 2 numbers - it is the smallest positive integer that is divisible by both numbers