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5th grade · Math · Unit 13 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.

New York State Learning Standards learning standard: NY-5.NF.1; NY-5.NF.2 · adding and subtracting fractions and mixed numbers with unlike denominators, including 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

Unlike Denominators in New York

In the New York State Learning Standards, this is unit 13 of 15 in 5th grade Math, after Multiply & Divide Fractions and before Volume of Boxes.

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: New York State Education Department (NYSED)

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

    Is 1/2 + 5/6 more or less than 1?

    • Less than 1
    • More than 1
    • Exactly 1

  2. Question 2

    What is 1/3 − 1/5?

    1/3 − 1/5 = ?

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

  3. Question 3

    Kenji walks 2/3 mile to the park and then 1/8 mile to the library. How far is that in all?

    • 3/11 mile
    • 5/6 mile
    • 19/24 mile
    • 19/48 mile

  4. Question 4

    What is 7/10 + 4/5?

    7/10 + 4/5 = ?

    • 3/2
    • 11/50
    • 11/15
    • 38/25

  5. Question 5

    What is 4 1/2 + 2 5/6?

    • 7 1/3
    • 8 1/3
    • 6 3/4
    • 6 1/3

  6. Question 6

    What is 1/5 + 1/2?

    1/5 + 1/2 = ?

    • 4/5
    • 2/7
    • 1/5
    • 7/10

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