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Solution - Least common multiple (LCM) by prime factorization

280
280

Step-by-step explanation

1. Find the prime factors of 7

7 is a prime factor.

2. Find the prime factors of 8

Tree view of the prime factors of 8: 2, 2 and 2

The prime factors of 8 are 2, 2 and 2.

3. Find the prime factors of 2

2 is a prime factor.

4. Find the prime factors of 5

5 is a prime factor.

5. Build a prime factors table

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

Prime factorNumber7 8 2 5 Max. occurrence
203103
500011
710001

The prime factors 5 and 7 occur one time, while 2 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 = 22257

LCM = 2357

LCM = 280

The least common multiple of 7, 8, 2 and 5 is 280.

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.