Adding Fractions with Unlike Denominators Worksheets
Add or subtract fractions with unlike denominators: free worksheets with boxes to rewrite each one and a key that shows every step. Print it or get a PDF.
Make free worksheets for adding (or subtracting) fractions with unlike denominators, written as stacked fractions like on paper. Choose related denominators (1/2 + 3/8), unrelated ones (2/3 + 1/4), or both, add boxes for rewriting each problem over a common denominator, and print an answer key that shows every step: 2/3 + 1/4 = 8/12 + 3/12 = 11/12.
Related: one denominator is a multiple of the other, so the larger one is the common denominator. Unrelated: find a new one (for 2/3 + 1/4, twelfths).
PDF puts the answer key on its own page.
Adding Fractions
10 problems · related and unrelated denominators
Name: ______________________ Date: ____________
Answer key
Answer Key · Adding Fractions
10 problems · related and unrelated denominators
How to use the adding fractions with unlike denominators worksheets
- 1Choose adding, subtracting, or both, and related, unrelated, or mixed denominators.
- 2Keep the common-denominator boxes on if students should rewrite each problem before solving.
- 3Press Regenerate for new problems, then print or download the PDF with its worked answer key.
- 4For two groups, choose 2 levels: related denominators first, then unrelated, each with its key.
When this is useful
Introducing unlike denominators
Start with related denominators (1/2 + 3/8), where the larger denominator is already the common one.
Practicing common denominators
Unrelated pairs like 2/3 + 1/4 make students find a new denominator (twelfths).
Showing the steps
The boxes under each problem ask for the rewritten fractions, not just the answer.
Checking work
The key shows the common denominator, the sum or difference, the simplified form, and the mixed number.
Two levels for small groups
One PDF with related denominators for one group and unrelated for another.
Examples to try
Related denominators
1/2 + 3/8 = 4/8 + 3/8 = 7/8.
Unrelated denominators
2/3 + 1/4 = 8/12 + 3/12 = 11/12.
An answer greater than 1
3/4 + 5/6 = 9/12 + 10/12 = 19/12 = 1 7/12.
Subtraction
5/6 − 1/4 = 10/12 − 3/12 = 7/12.
Tips for better results
Check if one denominator divides the other
For 1/3 + 5/6, sixths already work, so only one fraction needs rewriting.
Use the least common denominator
Any common denominator works, but the least one keeps numbers small and often avoids simplifying.
Only the numerators add
Once the denominators match, add or subtract the numerators and keep the denominator.
Simplify at the end
1/2 + 1/6 = 4/6, which simplifies to 2/3; the key shows both.
How the adding fractions with unlike denominators worksheets works
Every problem adds or subtracts two proper fractions with different denominators from 2 to 12, each already in lowest terms (so no 2/4 + 1/2 that is secretly like denominators). Related pairs have one denominator that is a multiple of the other; unrelated pairs don't. The least common denominator stays at 60 or less, and subtraction answers are always positive.
The answer key rewrites both fractions over the least common denominator, adds or subtracts, then simplifies and turns an answer greater than 1 into a mixed number: 3/4 + 5/6 = 9/12 + 10/12 = 19/12 = 1 7/12. The boxes on the student sheet follow the same steps.
Fractions are drawn stacked on screen and in the PDF, and everything is made on your device. Regenerate gives a new set; nothing is uploaded.
Private by design
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Frequently asked questions
How do you add fractions with unlike denominators?
Rewrite both fractions with a common denominator, then add the numerators. For 2/3 + 1/4, twelfths work: 2/3 = 8/12 and 1/4 = 3/12, so the sum is 11/12. Simplify at the end if you can.
What grade adds fractions with unlike denominators?
In the Common Core math standards used in many US states, adding and subtracting fractions with unlike denominators is a 5th grade skill (5.NF.A.1). In 4th grade, students add fractions with like denominators. Follow your own state's or program's standards.
What's the difference between related and unrelated denominators?
Related denominators are ones where one is a multiple of the other, like 2 and 8, so the larger one is the common denominator. Unrelated ones, like 3 and 4, need a new common denominator (12).
Are answers simplified?
Yes. The key shows the answer over the common denominator, then in lowest terms, then as a mixed number when it's more than 1.
Can I make subtraction worksheets?
Yes. Choose subtracting, or adding and subtracting. The first fraction is always the larger one, so answers are never negative.
Does it include mixed numbers in the problems?
No. Problems use proper fractions only; answers greater than 1 are shown as mixed numbers in the key.
Is it free?
Yes, with no account. Everything is made in your browser and nothing is uploaded.
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