Question
Find Least Common Multiple of 8, 12 and 15 using prime factorisation method.
Answer
LCM( 8, 12, 15 ) = 120
Explanation
Step 1: Write down factorisation of each number:
8 = 2 · 2 · 2
12 = 2 · 2 · 3
15 = 3 · 5
Step 2 : Match primes vertically:
| 8 | = | 2 | · | 2 | · | 2 | ||||
| 12 | = | 2 | · | 2 | · | 3 | ||||
| 15 | = | 3 | · | 5 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 8 | = | 2 | · | 2 | · | 2 | ||||||
| 12 | = | 2 | · | 2 | · | 3 | ||||||
| 15 | = | 3 | · | 5 | ||||||||
| LCM | = | 2 | · | 2 | · | 2 | · | 3 | · | 5 | = | 120 |
This solution can be visualized using a Venn diagram.
The LCM is equal to the product of all the numbers on the diagram.
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