What is the LCM of 21 and 28?
LCM of 6 and 8 is the least number which is exactly divisible by both 21 and 28.
Answer: LCM of 21 and 28 is 84
Lets see how to find the LCM of 21 and 28
Least Common Multiple or smallest common multiple also denoted by LCM of two integers a and b, usually denoted by lcm(a, b), is the smallest positive integer that is divisible by both a and b.
Below are some coomonly used methods used to find the LCM
Methods to Find LCM of 21 and 28
Let us use the following methods to find the LCM of 21 and 28
- Listing the Multiples
LCM of 21 and 28 by Listing Method
Here, we list the first few multiples of 21 and 28 and identify the common multiples.
The least among the common multiples is the LCM of 21 and 28
LCM of 21 and 28 by Formula
The formula of LCM is:
LCM(a,b) = ( a × b) / GCF (a,b)
The Greatest Common Factor of (21, 28) = 7
Thus, by substituting
LCM of 21 and 28 = (21 × 28) / 7
= 588/7 = 84
LCM of 21 and 28 = 84