Find Least Common Multiple of 3, 5, 4 and 7 using prime factorisation method.
Answer
LCM( 3, 5, 4, 7 ) = 420
Explanation
Step 1: Write down factorisation of each number:
3 = 3
5 = 5
4 = 2 · 2
7 = 7
Step 2 : Match primes vertically:
| 3 | = | 3 | ||||||||
| 5 | = | 5 | ||||||||
| 4 | = | 2 | · | 2 | ||||||
| 7 | = | 7 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 3 | = | 3 | ||||||||||
| 5 | = | 5 | ||||||||||
| 4 | = | 2 | · | 2 | ||||||||
| 7 | = | 7 | ||||||||||
| LCM | = | 2 | · | 2 | · | 3 | · | 5 | · | 7 | = | 420 |
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