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Solution - Least common multiple (LCM) by prime factorization

2,574
2,574

Step-by-step explanation

1. Find the prime factors of 13

13 is a prime factor.

2. Find the prime factors of 78

Tree view of the prime factors of 78: 2, 3 and 13

The prime factors of 78 are 2, 3 and 13.

3. Find the prime factors of 117

Tree view of the prime factors of 117: 3, 3 and 13

The prime factors of 117 are 3, 3 and 13.

4. Find the prime factors of 143

Tree view of the prime factors of 143: 11 and 13

The prime factors of 143 are 11 and 13.

5. Build a prime factors table

Determine the maximum number of times each prime factor (2, 3, 11, 13) occurs in the factorization of the given numbers:

Prime factorNumber13 78 117 143 Max. occurrence
201001
301202
1100011
1311111

The prime factors 2, 11 and 13 occur one time, while 3 occurs more than once.

6. Calculate the LCM

The least common multiple is the product of all factors in the greatest number of their occurrence.

LCM = 2331113

LCM = 2321113

LCM = 2,574

The least common multiple of 13, 78, 117 and 143 is 2,574.

Why learn this

The least common multiple (LCM), sometimes called the lowest common multiple or least common divisor, is helpful for understanding the relationships between numbers. For example, if it takes Earth 365 days to orbit the sun and it takes Venus 225 days to orbit the sun and both are in perfect alignment at the time this scenario is given, how long will it take for Earth and Venus to align again? We can use LCM to determine that the answer would be 16,425 days.

LCM is also a very important part of many mathematical concepts that also have real-world applications. For example, we use LCMs when adding and subtracting fractions, which we use quite frequently.