LCM( 3, 12, 7, 5 ) = 420
Step 1: Write down factorisation of each number:
3 = 3
12 = 2 · 2 · 3
7 = 7
5 = 5
Step 2 : Match primes vertically:
3 | = | 3 | ||||||||
12 | = | 2 | · | 2 | · | 3 | ||||
7 | = | 7 | ||||||||
5 | = | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
3 | = | 3 | ||||||||||
12 | = | 2 | · | 2 | · | 3 | ||||||
7 | = | 7 | ||||||||||
5 | = | 5 | ||||||||||
LCM | = | 2 | · | 2 | · | 3 | · | 5 | · | 7 | = | 420 |