LCM( 4, 7, 3, 5 ) = 420
Step 1: Write down factorisation of each number:
4 = 2 · 2
7 = 7
3 = 3
5 = 5
Step 2 : Match primes vertically:
4 | = | 2 | · | 2 | ||||||
7 | = | 7 | ||||||||
3 | = | 3 | ||||||||
5 | = | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
4 | = | 2 | · | 2 | ||||||||
7 | = | 7 | ||||||||||
3 | = | 3 | ||||||||||
5 | = | 5 | ||||||||||
LCM | = | 2 | · | 2 | · | 3 | · | 5 | · | 7 | = | 420 |