Math – Subtracting Fractions (Part 1)

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     When subtracting fractions, you have to find a common denominator in the same way as you would by adding fractions.  The major difference though is that this time, you subtract the numerators.

     We will use a similar example to the one we did with adding fractions.  Assume you have 6 slices of pizza.  You decide to give your friend 4 pieces (which is 4/6).  We can use fractions to illustrate this point:

     6/6 – 4/6 = 2/6 

     When the denominators are the same (in this case 6 and 6) all we have to do is subtract the numerators (in this case 6-4=2).

     What if the denominators are different?

     In order to subtract fractions with different denominators we must first find a common denominator (much like we did when we added fractions with different denominators).

    Let’s assume you have ⅝ of a candy bar and you want to give away ¼.

     First, we find a common denominator.

     When we look at ⅝ and ¼, we can see that 8 will go into itself once, and 4 will go into 8 two times.

     Since 8 x 1 = 8, we do the same to the numerator, 5 x 1 = 5.

     Since 4 x 2 = 8, we do the same to the numerator, 1 x 2 = 2.

     Now we have a new fraction and equation:  5/8 – 2/8

     The answer is ⅜.

     If you are trying to help your child subtract fractions, first look at the denominators.  If they are the same, simply subtract the numerators.  If they are different, find a common denominator and make them the same.

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