Subscribe

5th grade · Math · Unit 14 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.

Alabama Course of Study content standard: 5.9; 5.10 · 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

Unlike Denominators in Alabama

In the Alabama Course of Study, this is unit 14 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: Alabama State Department of Education (ALSDE)

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 3/8 + 4 7/10?

    • 8 3/40
    • 9 3/40
    • 7 3/40
    • 7 5/9

  2. Question 2

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

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

  3. Question 3

    What is 1/3 + 3/4?

    1/3 + 3/4 = ?

    • 7/6
    • 13/12
    • 1/3
    • 4/7

  4. Question 4

    What is 1/3 − 1/4?

    1/3 − 1/4 = ?

    • 1/12
    • 1/6
    • 7/12
    • 0

  5. Question 5

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

    • Exactly 1
    • More than 1
    • Less than 1

  6. Question 6

    What is 5/12 − 1/4?

    5/12 − 1/4 = ?

    • 3/16
    • 1/12
    • 1/6
    • 1/2

More 5th grade