Find Least Common Multiple of 30, 70 and 105 using prime factorisation method.
Answer
LCM( 30, 70, 105 ) = 210
Explanation
Step 1: Write down factorisation of each number:
30 = 2 · 3 · 5
70 = 2 · 5 · 7
105 = 3 · 5 · 7
Step 2 : Match primes vertically:
| 30 | = | 2 | · | 3 | · | 5 | ||
| 70 | = | 2 | · | 5 | · | 7 | ||
| 105 | = | 3 | · | 5 | · | 7 |
Step 3 : Bring down numbers in each column and multiply to get LCM:
| 30 | = | 2 | · | 3 | · | 5 | ||||
| 70 | = | 2 | · | 5 | · | 7 | ||||
| 105 | = | 3 | · | 5 | · | 7 | ||||
| LCM | = | 2 | · | 3 | · | 5 | · | 7 | = | 210 |
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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