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Solution - Least common multiple (LCM) by prime factorization

7,560
7,560

Step-by-step explanation

1. Find the prime factors of 15

Tree view of the prime factors of 15: 3 and 5

The prime factors of 15 are 3 and 5.

2. Find the prime factors of 18

Tree view of the prime factors of 18: 2, 3 and 3

The prime factors of 18 are 2, 3 and 3.

3. Find the prime factors of 24

Tree view of the prime factors of 24: 2, 2, 2 and 3

The prime factors of 24 are 2, 2, 2 and 3.

4. Find the prime factors of 27

Tree view of the prime factors of 27: 3, 3 and 3

The prime factors of 27 are 3, 3 and 3.

5. Find the prime factors of 56

Tree view of the prime factors of 56: 2, 2, 2 and 7

The prime factors of 56 are 2, 2, 2 and 7.

6. Build a prime factors table

Determine the maximum number of times each prime factor (2, 3, 5, 7) occurs in the factorization of the given numbers:

Prime factorNumber15 18 24 27 56 Max. occurrence
2013033
3121303
5100001
7000011

The prime factors 5 and 7 occur one time, while 2 and 3 occur more than once.

7. Calculate the LCM

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

LCM = 22233357

LCM = 233357

LCM = 7,560

The least common multiple of 15, 18, 24, 27 and 56 is 7,560.

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.