LCM( 4, 20, 15, 5, 3 ) = 60
Step 1: Write down factorisation of each number:
4 = 2 · 2
20 = 2 · 2 · 5
15 = 3 · 5
5 = 5
3 = 3
Step 2 : Match primes vertically:
4 | = | 2 | · | 2 | ||||
20 | = | 2 | · | 2 | · | 5 | ||
15 | = | 3 | · | 5 | ||||
5 | = | 5 | ||||||
3 | = | 3 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
4 | = | 2 | · | 2 | ||||||
20 | = | 2 | · | 2 | · | 5 | ||||
15 | = | 3 | · | 5 | ||||||
5 | = | 5 | ||||||||
3 | = | 3 | ||||||||
LCM | = | 2 | · | 2 | · | 3 | · | 5 | = | 60 |