How to Add and Subtract Fractions
When the bottom numbers are the same, add or subtract the top numbers.
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How to do it
- Check that the bottom numbers are the same.
- Add or subtract the top numbers.
- Keep the bottom number.
Teaching tip
Say each problem in words, like "3 eighths plus 2 eighths," so it is clear the bottom number names the size of the pieces. This sheet is aligned with Common Core 4.NF.B.3.
About this chart
Worked examples with strips: 3/8 + 2/8, 7/10 − 4/10, and 1 − 3/8 by writing 1 as 8/8, with why the bottom number never changes.
What kids practice
When fractions have the same bottom number, the pieces are the same size, so you add or subtract just the top numbers: 3/8 + 2/8 = 5/8. Fourth graders also break fractions apart into sums, change between mixed numbers like 2 3/4 and improper fractions like 11/4, and add and subtract mixed numbers.
Watch for
- Adding the bottom numbers too, like 3/8 + 2/8 = 5/16.
- Forgetting to trade when the fraction part is more than 1, like writing 3 5/4.
- Subtracting the smaller top number from the bigger one when regrouping is needed in mixed numbers.
- Mixing up the whole number and the remainder when changing an improper fraction to a mixed number.
It's free to print, as many copies as you need. See the full adding and subtracting fractions guide for 4th grade.
More sheets in this set
- See it all
1. How to Break Apart a Fraction5/8 broken into single eighths and into groups two different ways, and the mixed number 2 1/8 written as 8/8 + 8/8 + 1/8. 
2. Break Apart a FractionFractions to write as a sum two different ways, like 5/8 = 2/8 + 3/8. More adds mixed numbers, like 1 3/8 = 8/8 + 3/8. Many answers are right.
4. Add FractionsAdding fractions with the same bottom number on graph paper. Fewer shows both parts on the strip, Standard has a strip to shade, and More adds three fractions, sums more than 1, and hundredths.
5. Subtract FractionsSubtracting fractions with the same bottom number on graph paper. Fewer shows the crossed-out parts, Standard has a strip to cross out, and More adds 1 minus a fraction, improper fractions and hundredths.- See it all
6. How to Change Mixed Numbers and Improper FractionsStep-by-step worked examples changing 2 3/4 to 11/4 and 14/5 to 2 4/5, with circle pictures to check. 
7. Mixed Numbers and Improper FractionsChanging mixed numbers like 2 3/4 to improper fractions like 11/4, and back. Fewer has circle pictures, and More uses bigger whole numbers.- See it all
8. How to Add and Subtract Mixed NumbersWorked examples of 1 3/4 + 2 2/4 with trading 4/4 for a whole, and 3 1/4 − 1 3/4 with trading a whole for 4/4. 
9. Add and Subtract Mixed NumbersAdding and subtracting mixed numbers with the same bottom number on graph paper, with rows to work in. Fewer and Standard have no regrouping, and More adds regrouping.
10. Fraction Word ProblemsStories about pizza, flour, walking, ribbon, paint, juice and reading with fractions that have the same bottom number. More adds mixed numbers.