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Solution - Least common multiple (LCM) by prime factorization

4,620
4,620

Step-by-step explanation

1. 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.

2. Find the prime factors of 132

Tree view of the prime factors of 132: 2, 2, 3 and 11

The prime factors of 132 are 2, 2, 3 and 11.

3. Find the prime factors of 140

Tree view of the prime factors of 140: 2, 2, 5 and 7

The prime factors of 140 are 2, 2, 5 and 7.

4. Find the prime factors of 330

Tree view of the prime factors of 330: 2, 3, 5 and 11

The prime factors of 330 are 2, 3, 5 and 11.

5. Build a prime factors table

Determine the maximum number of times each prime factor (2, 3, 5, 7, 11) occurs in the factorization of the given numbers:

Prime factorNumber42 132 140 330 Max. occurrence
212212
311011
500111
710101
1101011

The prime factors 3, 5, 7 and 11 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 = 2235711

LCM = 2235711

LCM = 4,620

The least common multiple of 42, 132, 140 and 330 is 4,620.

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.