LCM( 6, 9, 15, 20 ) = 180
Step 1: Write down factorisation of each number:
6 = 2 · 3
9 = 3 · 3
15 = 3 · 5
20 = 2 · 2 · 5
Step 2 : Match primes vertically:
6 | = | 2 | · | 3 | ||||||
9 | = | 3 | · | 3 | ||||||
15 | = | 3 | · | 5 | ||||||
20 | = | 2 | · | 2 | · | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
6 | = | 2 | · | 3 | ||||||||
9 | = | 3 | · | 3 | ||||||||
15 | = | 3 | · | 5 | ||||||||
20 | = | 2 | · | 2 | · | 5 | ||||||
LCM | = | 2 | · | 2 | · | 3 | · | 3 | · | 5 | = | 180 |