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Solution - Least common multiple (LCM) by prime factorization

10,710
10,710

Step-by-step explanation

1. Find the prime factors of 35

Tree view of the prime factors of 35: 5 and 7

The prime factors of 35 are 5 and 7.

2. Find the prime factors of 42

Tree view of the prime factors of 42: 2, 3 and 7

The prime factors of 42 are 2, 3 and 7.

3. Find the prime factors of 51

Tree view of the prime factors of 51: 3 and 17

The prime factors of 51 are 3 and 17.

4. Find the prime factors of 63

Tree view of the prime factors of 63: 3, 3 and 7

The prime factors of 63 are 3, 3 and 7.

5. Build a prime factors table

Determine the maximum number of times each prime factor (2, 3, 5, 7, 17) occurs in the factorization of the given numbers:

Prime factorNumber35 42 51 63 Max. occurrence
201001
301122
510001
711011
1700101

The prime factors 2, 5, 7 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 = 2335717

LCM = 2325717

LCM = 10,710

The least common multiple of 35, 42, 51 and 63 is 10,710.

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.