Find Least Common Multiple of 42, 60 and 78 using prime factorisation method.
Answer
LCM( 42, 60, 78 ) = 5460
Explanation
Step 1: Write down factorisation of each number:
42 = 2 · 3 · 7
60 = 2 · 2 · 3 · 5
78 = 2 · 3 · 13
Step 2 : Match primes vertically:
| 42 | = | 2 | · | 3 | · | 7 | ||||||
| 60 | = | 2 | · | 2 | · | 3 | · | 5 | ||||
| 78 | = | 2 | · | 3 | · | 13 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 42 | = | 2 | · | 3 | · | 7 | ||||||||
| 60 | = | 2 | · | 2 | · | 3 | · | 5 | ||||||
| 78 | = | 2 | · | 3 | · | 13 | ||||||||
| LCM | = | 2 | · | 2 | · | 3 | · | 5 | · | 7 | · | 13 | = | 5460 |
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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