lcm calculation method

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LCM


LCM stands for least common multiple.

LCM of two numbers is the smallest number that is a multiple of both the given numbers.

Example

What is the LCM of 4 and 6?
Multiples of 4 are: 4, 8, 12, 16, 20, 24, 28, 32, 36, 40, 44, 48, 52, 56, 60, 64, 68, 72, 76
Multiples of 6 are: 6, 12, 18, 24, 30, 36, 42, 48, 54, 60, 66, 72
Common multiples of 4 and 6 are simply the numbers that are in both lists: 12, 24, 36, 48, 60, 72, ....
So the least common multiple of 4 and 6 is the smallest one of those: 12

Lcm by prime factorization

Find LCM of 30 and 45.

1. First list the prime factors of each number.
30 = 2*3*5 45 = 3*3*5
2. Underline the common factors.
3. The LCM = (the common factors written once) * (the non common factors)
4. Here, LCM = (5*3) * (2*3)
= 2*3*3*5 = 90 i.e. LCM of 30 and 45.