Add or subtract fractions using parts of the same size. Start with like denominators, move to unlike denominators, or choose signed fractions for a later extension.
Use the worksheet to show the intermediate equivalent fractions, not just the final answer. The matching key gives a simplified result so the calculation can be checked after the learner has explained the method.
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When the parts already have the same size, combine or remove the counted parts: 1/5 + 2/5 = 3/5. For subtraction, 5/8 − 1/8 = 4/8 = 1/2. The denominator describes the size of each part and does not get added.
For 1/3 + 1/4, use twelfths: 4/12 + 3/12 = 7/12. A common denominator can be a shared multiple of the original denominators; it does not have to be their product when a smaller shared multiple works.
Like-denominator work is a fourth-grade starting point. General unlike-denominator addition and subtraction are fifth-grade tasks. The signed-fraction level extends the arithmetic to positive and negative values in seventh grade.
Check the sign and approximate size of an answer. Adding two positive fractions must produce a number larger than either addend. Adding numerators and denominators separately, such as writing 1/3 + 1/4 = 2/7, does not preserve the quantities.