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5th grade · Math · Unit 13 of 14

Unlike Denominators

Add fractions with different bottoms

What your child practices

Adding and subtracting fractions and mixed numbers with different denominators by finding a common denominator, and checking with benchmark fractions.

Oregon State Standards learning standard: 5.NF.A.1; 5.NF.A.2 · adding and subtracting fractions and mixed numbers with unlike denominators, including in word problems

How we explain it

Children can open this short lesson before they practice.

  1. Find a common denominator.
  2. Rename each fraction with that denominator.
  3. Add or subtract the tops. Keep the bottom. Simplify.

Example: What is 1/2 + 1/3? Common denominator: 6. 1/2 = 3/6 and 1/3 = 2/6. 3/6 + 2/6 = 5/6. Answer: 5/6

Sample questions

A taste of this unit. In the app, questions change every time and get easier or harder to match your child.

  1. Question 1

    What is 1/3 − 1/5?

    1/3 − 1/5 = ?

    • 2/15
    • 8/15
    • 0
    • 1/5

  2. Question 2

    Amir walks 1/3 mile to the park and then 1/2 mile to the library. How far is that in all?

    • 1 mile
    • 5/12 mile
    • 5/6 mile
    • 2/5 mile

  3. Question 3

    What is 4 1/3 + 4 2/5?

    • 9 11/15
    • 8 3/8
    • 7 11/15
    • 8 11/15

  4. Question 4

    What is 1/2 + 3/8?

    1/2 + 3/8 = ?

    • 1/4
    • 2/5
    • 15/16
    • 7/8

  5. Question 5

    Is 3/4 + 5/6 more or less than 1?

    • More than 1
    • Less than 1
    • Exactly 1

  6. Question 6

    What is 3/4 + 1/5?

    3/4 + 1/5 = ?

    • 19/20
    • 1
    • 4/9
    • 1/5

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