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Solution - Least common multiple (LCM) by prime factorization

27,846
27,846

Step-by-step explanation

1. Find the prime factors of 102

Tree view of the prime factors of 102: 2, 3 and 17

The prime factors of 102 are 2, 3 and 17.

2. 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.

3. Find the prime factors of 119

Tree view of the prime factors of 119: 7 and 17

The prime factors of 119 are 7 and 17.

4. Find the prime factors of 221

Tree view of the prime factors of 221: 13 and 17

The prime factors of 221 are 13 and 17.

5. Build a prime factors table

Determine the maximum number of times each prime factor (2, 3, 7, 13, 17) occurs in the factorization of the given numbers:

Prime factorNumber102 117 119 221 Max. occurrence
210001
312002
700101
1301011
1710111

The prime factors 2, 7, 13 and 17 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 = 23371317

LCM = 23271317

LCM = 27,846

The least common multiple of 102, 117, 119 and 221 is 27,846.

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.