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Chapter 2 · Fractions · page 9 of 68

Adding and subtracting fractions

levelGrade 5
standard5.NF.A.1
practiceFraction operations

You can only add pieces of the same size. If the bottoms match, add the tops and keep the bottom. If they do not, rewrite each fraction over a common bottom first.

How to use it

  1. Same bottom: add or subtract the tops. Keep the bottom.
  2. Different bottoms: find a number both bottoms divide into. The smallest one keeps the numbers small, but any common one works.
  3. Rewrite each fraction over it, then add the tops.
  4. Simplify if you can.

Example

16+56=66=1\frac{1}{6} + \frac{5}{6} = \frac{6}{6} = 1
12+13=36+26=56\frac{1}{2} + \frac{1}{3} = \frac{3}{6} + \frac{2}{6} = \frac{5}{6}

Where it goes wrong

  • Adding the bottoms. 1/2 + 1/3 is not 2/5. Pieces of different sizes cannot be counted together.
  • Changing the bottom without changing the top to match.

Related

Equivalent fractions and simplest formMultiplying fractionsMixed numbers and improper fractions
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