LCM( 21, 17, 39 ) = 4641
Step 1: Write down factorisation of each number:
21 = 3 · 7
17 = 17
39 = 3 · 13
Step 2 : Match primes vertically:
21 | = | 3 | · | 7 | ||||
17 | = | 17 | ||||||
39 | = | 3 | · | 13 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
21 | = | 3 | · | 7 | ||||||
17 | = | 17 | ||||||||
39 | = | 3 | · | 13 | ||||||
LCM | = | 3 | · | 7 | · | 13 | · | 17 | = | 4641 |
This solution can be visualized using a Venn diagram.
The LCM is equal to the product of all the numbers on the diagram.