# Lowest Common Denominator (LCD) of 1/1 and 21/84

So you wanna find the lowest common denominator of 1/1 and 21/84? Lucky for you that's exactly what this page is here to help you with! In this quick guide, we'll walk you through how to calculate the lowest common denominator for any fractions you need to check. Here we go!

In a rush and just want the answer? No worries! The LCD of 1/1 and 21/84 is 84. In fraction form it's **1/84**.

LCD(1/1, 21/84) = 84

In fraction form:

Read on to find out how we worked that out!

As we always do in these articles, it's worth a very quick recap on fraction terminology. The number above the line is called the numerator and the number about the line is called the denominator. So, in this example, our numerators are 1 and 21, while our denominators are 1 and 84.

## What is the Lowest Common Denominator?

To calculate the lowest common denominator, the easiest way is to look at the factors of those numbers and find the lowest common multiple. Here's how that looks for 1 and 84:

- Factors for 1: 1
- Factors for 84: 1, 2, 3, 4, 6, 7, 12, 14, 21, 28, 42, and
**84**

The next step is to calculate the numerator and complete our fraction. To do this, we need to find the greatest common factor of the numerators, which are 1 and 21.

- Factors for 1:
**1** - Factors for 21:
**1**, 3, 7, and 21

As we can see, the greatest common factor between the numerators is 1, so this becomes our numerator in the fraction:

Hopefully this article has helped you to understand how to calculate the lowest common denominator of two fractions. Isn't math fun? If you want to challenge yourself, try to work out the least common denominator of some fractions by yourself and use our LCD calculator to check your answers!

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