# How to Calculate 1/1 Minus 21/78

Are you looking to work out and calculate how to subtract 1/1 from 21/78? In this really simple guide, we'll teach you exactly what 1/1 - 21/78 is and walk you through the step-by-process of how to subtract one fraction from another.

Want to quickly learn or show students how to calculate 1/1 minus 21/78? Play this very quick and fun video now!

To start with, the number above the line in a fraction is called a numerator and the number below the line is called the denominator.

Why do you need to know this? Well, because to subtract a fractions from another we need to first make sure both fractions have the same denominator.

Let's set up 1/1 and 21/78 side by side so they are easier to see:

Our denominators are 1 and 78. What we need to do is find the lowest common denominator of the two numbers, which is 78 in this case.

If we multiply the first denominator (1) by 78 we will get 78. If we we multiply the second denominator (78) by 1 we will also get 78. We also need to multiply the numerators above the line by the same amounts so that the fraction values are correct:

This is what 1/1 minus 21/78 looks like with the same denominator:

Now that these fractions have been converted to have the same denominator, we can subtract one numerator from the other to make one fraction:

You're done! You now know exactly how to calculate 1/1 - 21/78. Hopefully you understood the process and can use the same techniques to add other fractions together. The complete answer is below (simplified to the lowest form):

## Convert 1/1 minus 21/78 to Decimal

Here's a little bonus calculation for you to easily work out the decimal format of the fraction we calculated. All you need to do is divide the numerator by the denominator and you can convert any fraction to decimal:

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