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Solution - Least common multiple (LCM) by prime factorization

48,510
48,510

Step-by-step explanation

1. Find the prime factors of 77

Tree view of the prime factors of 77: 7 and 11

The prime factors of 77 are 7 and 11.

2. 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.

3. Find the prime factors of 98

Tree view of the prime factors of 98: 2, 7 and 7

The prime factors of 98 are 2, 7 and 7.

4. Find the prime factors of 105

Tree view of the prime factors of 105: 3, 5 and 7

The prime factors of 105 are 3, 5 and 7.

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 factorNumber77 63 98 105 Max. occurrence
200101
302012
500011
711212
1110001

The prime factors 2, 5 and 11 occur one time, while 3 and 7 occur 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 = 23357711

LCM = 23257211

LCM = 48,510

The least common multiple of 77, 63, 98 and 105 is 48,510.

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.