Question
Find Least Common Multiple of 8, 9, 25 and 7 using prime factorisation method.
Answer
LCM( 8, 9, 25, 7 ) = 12600
Explanation
Step 1: Write down factorisation of each number:
8 = 2 · 2 · 2
9 = 3 · 3
25 = 5 · 5
7 = 7
Step 2 : Match primes vertically:
| 8 | = | 2 | · | 2 | · | 2 | ||||||||||
| 9 | = | 3 | · | 3 | ||||||||||||
| 25 | = | 5 | · | 5 | ||||||||||||
| 7 | = | 7 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 8 | = | 2 | · | 2 | · | 2 | ||||||||||||
| 9 | = | 3 | · | 3 | ||||||||||||||
| 25 | = | 5 | · | 5 | ||||||||||||||
| 7 | = | 7 | ||||||||||||||||
| LCM | = | 2 | · | 2 | · | 2 | · | 3 | · | 3 | · | 5 | · | 5 | · | 7 | = | 12600 |
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