How to Multiply and Divide Fractions in Algebra
 
How to Add and Subtract Fractions in Algebra
 
How to Use Prime Factorization on Composite Numbers
 

How to Subtract Fractions

You can subtract proper fractions that have different denominators — such as thirds and sixths — if you find the common denominator first. The biggest step in subtracting proper fractions is finding the common denominator, but once you've done that, you can subtract the numerators just like any other basic subtraction problem.

Example: In her will, Jane gave 4/7 of her money to the Humane Society and 1/3 of her money to other charities. How much was left for her children’s inheritance?

  1. Convert the fractions so that they have the same number in the denominators.

    image0.png

    Can you spot the common denominator among all those fractions? Both fractions have a common denominator, 21. So now,

    image1.png
  2. Add or subtract the numerators, and leave the denominators alone.

    Add the numerators to get the total designation to charity in Jane's will:

    image2.png

    Subtract that result from the whole of Jane’s money (21/21) to determine the portion allotted to her children:

    image3.png
  3. Reduce the answer, if needed.

    In this case, 2/21 is the answer — the amount of Jane's estate that Jane's children will be awarded — and the answer doesn't need to be reduced.

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Algebra's Rules of Divisibility
How to Change Improper Fractions to Mixed Numbers
How Proper Fractions Work
How to Convert Fractions to Decimals
How to Create Equivalent Fractions Using Common Denominators
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