Question
Find Least Common Multiple of 42, 140, 8 and 62 using prime factorisation method.
Answer
LCM( 42, 140, 8, 62 ) = 26040
Explanation
Step 1: Write down factorisation of each number:
42 = 2 · 3 · 7
140 = 2 · 2 · 5 · 7
8 = 2 · 2 · 2
62 = 2 · 31
Step 2 : Match primes vertically:
| 42 | = | 2 | · | 3 | · | 7 | ||||||||
| 140 | = | 2 | · | 2 | · | 5 | · | 7 | ||||||
| 8 | = | 2 | · | 2 | · | 2 | ||||||||
| 62 | = | 2 | · | 31 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 42 | = | 2 | · | 3 | · | 7 | ||||||||||
| 140 | = | 2 | · | 2 | · | 5 | · | 7 | ||||||||
| 8 | = | 2 | · | 2 | · | 2 | ||||||||||
| 62 | = | 2 | · | 31 | ||||||||||||
| LCM | = | 2 | · | 2 | · | 2 | · | 3 | · | 5 | · | 7 | · | 31 | = | 26040 |
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