Question
Find Least Common Multiple of 12, 24, 48 and 72 using ladder method..
Answer
LCM( 12, 24, 48, 72 ) = 144
Explanation
Step 1 : Place the numbers inside division bar:
| 12 | 24 | 48 | 72 |
Step 2 : Find a prime number which can divide at least two of your numbers.
In this example we can divide by 2. If any number is not divisible by 2 write it down unchanged.
| 2 | 12 | 24 | 48 | 72 |
| 6 | 12 | 24 | 36 |
Step 3 : Repeat Step 2 until you can no longer divide.
| 2 | 12 | 24 | 48 | 72 |
| 2 | 6 | 12 | 24 | 36 |
| 3 | 6 | 12 | 18 |
| 2 | 12 | 24 | 48 | 72 |
| 2 | 6 | 12 | 24 | 36 |
| 2 | 3 | 6 | 12 | 18 |
| 3 | 3 | 6 | 9 |
| 2 | 12 | 24 | 48 | 72 |
| 2 | 6 | 12 | 24 | 36 |
| 2 | 3 | 6 | 12 | 18 |
| 3 | 3 | 3 | 6 | 9 |
| 1 | 1 | 2 | 3 |
Since there are no primes that divides at least two of given numbers, we conclude that the LCM is a product of starting numbers.
LCM = 12 · 24 · 48 · 72 = 144
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