Question
Find Least Common Multiple of 7, 14, 12 and 4 using prime factorisation method.
Answer
LCM( 7, 14, 12, 4 ) = 84
Explanation
Step 1: Write down factorisation of each number:
7 = 7
14 = 2 · 7
12 = 2 · 2 · 3
4 = 2 · 2
Step 2 : Match primes vertically:
| 7 | = | 7 | ||||||
| 14 | = | 2 | · | 7 | ||||
| 12 | = | 2 | · | 2 | · | 3 | ||
| 4 | = | 2 | · | 2 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 7 | = | 7 | ||||||||
| 14 | = | 2 | · | 7 | ||||||
| 12 | = | 2 | · | 2 | · | 3 | ||||
| 4 | = | 2 | · | 2 | ||||||
| LCM | = | 2 | · | 2 | · | 3 | · | 7 | = | 84 |
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