Addition of Fractions with Unlike Denominators

Examples, solutions, and videos to help Grade 4 students learn how use visual models to add two fractions with related units using the denominators 2, 3, 4, 5, 6, 8, 10, and 12.

Common Core Standards: 4.NF.3a, 4.NF.3d, 4.NF.1, 4.MD.2

NYS Common Core Grade 4 Module 5, Lesson 21

Worksheets for Grade 4

Lesson 21 Concept Development
Problem 1: Add two fractions with related units modeled with a tape diagram. Use a number bond to rename the sum as a mixed number.
3/8 + 3/4 =

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Lesson 21 Problem Set

1. Draw a tape diagram to represent each addend. Decompose one of the tape diagrams to make like units. Then write a complete number sentence. Use a number bond to write each sum as a mixed number.
   a. 3/4 + 1/2
   b. 2/3 + 3/6
   c. 5/6 + 1/3
   d. 4/5 + 7/10
2. Draw a number line to model the addition. Then write a complete number sentence. Use a number bond to write each sum as a mixed number.
   a. 1/2 + 3/4
   b. 1/2 + 6/8
   c. 7/10 + 3/5
   d. 2/3 + 5/6
3. Solve. Write the sum as a mixed number. Draw a model if needed.
   a. 3/4 + 2/8
   b. 4/6 + 1/2
   c. 4/6 + 2/3
   d. 8/10 + 3/5
   e. 5/8 + 3/4
   f. 5/8 + 2/4
   g. 1/2 + 5/8
   h. 3/10 + 4/5

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Lesson 21 Homework

1. Draw a tape diagram to represent each addend. Decompose one of the tape diagrams to make like units. Then write a complete number sentence. Use a number bond to write each sum as a mixed number.
   a. 7/8 + 1/4
   b. 4/8 + 2/4
   c. 4/6 + 1/2
   d. 3/5 + 8/10
2. Draw a number line to model the addition. Then write a complete number sentence. Use a number bond to write each sum as a mixed number.
   a. 1/2 + 5/8
   b. 3/4 + 3/8
   c. 4/10 + 4/5
   d. 1/3 + 5/6
3. Solve. Write the sum as a mixed number. Draw a model if needed.
   a. 1/2 + 6/6
   b. 7/8 + 3/4
   c. 5/6 + 1/3
   d. 9/10 + 2/5
   e. 4/12 + 3/4
   f. 1/2 + 5/6
   g. 3/12 + 5/6
   h. 7/10 + 4/5

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