How do you get the lcd or least common denominator?

Answer 1

The LCD (Lowest Common Denominator) is the lowest number which, divided with a given set of numbers, yields no remainder.

Take this set of numbers:

{2, 6, 30}

The lcd for the set can be obtained by rewriting the numbers as prime factors.

2 is already prime.

6 isn't prime and can be written as 2*3 (both primes).

30 isn't prime and can be written as 2*3*5 (all primes).

By looking at the prime factors we see that the numbers have a common divisor, 2.

Divide all numbers by the common common divisor and we get:

{1,3,15}

Multiply these together to get:

1*3*15 = 45

This is the LCD for {2, 6, 30}.

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So, as a quick recap:

• Find the GCD (Greatest Common Divisor) of the numbers through prime factorization.
• Divide the numbers by the GCD.
• Multiply the numbers together to get the LCD.

Answer 2

Example: 1/30 and 1/42
Factor them.
2 x 3 x 5 = 30
2 x 3 x 7 = 42
Combine the factors, eliminating duplicates.
2 x 3 x 5 x 7 = 210, the LCD

Answer 3

Example: 1/30 and 1/42

Factor them.

2 x 3 x 5 = 30

2 x 3 x 7 = 42

Select the highest amount of each factor.

2 x 3 x 5 x 7 = 210, the LCD