Question
Find Least Common Multiple of 105, 100, 21 and 10 using prime factorisation method.
Answer
LCM( 105, 100, 21, 10 ) = 2100
Explanation
Step 1: Write down factorisation of each number:
105 = 3 · 5 · 7
100 = 2 · 2 · 5 · 5
21 = 3 · 7
10 = 2 · 5
Step 2 : Match primes vertically:
| 105 | = | 3 | · | 5 | · | 7 | ||||||
| 100 | = | 2 | · | 2 | · | 5 | · | 5 | ||||
| 21 | = | 3 | · | 7 | ||||||||
| 10 | = | 2 | · | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 105 | = | 3 | · | 5 | · | 7 | ||||||||
| 100 | = | 2 | · | 2 | · | 5 | · | 5 | ||||||
| 21 | = | 3 | · | 7 | ||||||||||
| 10 | = | 2 | · | 5 | ||||||||||
| LCM | = | 2 | · | 2 | · | 3 | · | 5 | · | 5 | · | 7 | = | 2100 |
This page was created using
LCM Calculator