Find Least Common Multiple of 1, 20, 22 and 5 using prime factorisation method.
Answer
LCM( 1, 20, 22, 5 ) = 220
Explanation
Step 1: Write down factorisation of each number:
1 = 1
20 = 2 · 2 · 5
22 = 2 · 11
5 = 5
Step 2 : Match primes vertically:
| 1 | = | 1 | ||||||||
| 20 | = | 2 | · | 2 | · | 5 | ||||
| 22 | = | 2 | · | 11 | ||||||
| 5 | = | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 1 | = | 1 | ||||||||||
| 20 | = | 2 | · | 2 | · | 5 | ||||||
| 22 | = | 2 | · | 11 | ||||||||
| 5 | = | 5 | ||||||||||
| LCM | = | 1 | · | 2 | · | 2 | · | 5 | · | 11 | = | 220 |
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