LCM( 10, 5, 4, 20 ) = 20
Step 1: Write down factorisation of each number:
10 = 2 · 5
5 = 5
4 = 2 · 2
20 = 2 · 2 · 5
Step 2 : Match primes vertically:
10 | = | 2 | · | 5 | ||
5 | = | 5 | ||||
4 | = | 2 | · | 2 | ||
20 | = | 2 | · | 2 | · | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
10 | = | 2 | · | 5 | ||||
5 | = | 5 | ||||||
4 | = | 2 | · | 2 | ||||
20 | = | 2 | · | 2 | · | 5 | ||
LCM | = | 2 | · | 2 | · | 5 | = | 20 |