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5th grade · Math · Unit 4 of 15

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.

Texas Essential Knowledge and Skills (TEKS) teks student expectation: 5.3(H); 5.3(K) · adding and subtracting fractions with unequal denominators

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

Unlike Denominators in Texas

In the Texas Essential Knowledge and Skills (TEKS), this is unit 4 of 15 in 5th grade Math, after Divide and before Prime Factor Trees.

Gradelings describes a child's practice on this unit as Beginning, Approaching, Meeting or Exceeding (Four practice steps). That reflects practice, not a report-card mark: the teacher decides the mark.

Source: Texas Education Agency (TEA)

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 3/8 + 1/2?

    3/8 + 1/2 = ?

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

  2. Question 2

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

    • 4 1/4
    • 3 2/3
    • 3 1/4
    • 5 1/4

  3. Question 3

    Noah walks 1/4 mile to the park and then 1/6 mile to the library. How far is that in all?

    • 5/12 mile
    • 1/5 mile
    • 11/24 mile
    • 5/24 mile

  4. Question 4

    What is 3/4 − 1/5?

    3/4 − 1/5 = ?

    • 3/5
    • 1/10
    • 2
    • 11/20

  5. Question 5

    Is 2/3 + 1/2 more or less than 1?

    • Less than 1
    • More than 1
    • Exactly 1

  6. Question 6

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

    • 6 9/10
    • 5 9/10
    • 6 3/7
    • 7 9/10

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