Free worksheets · Grade 5
Adding Fractions with Unlike Denominators Worksheet
Find a common denominator, rewrite each fraction, add the numerators, and simplify.
Free printable
Adding Fractions with Unlike Denominators
15 questions, one page, US Letter. Print it and do it on paper.
On the sheet: Find a common denominator: the smallest number both denominators divide into. Rewrite each fraction with that denominator, multiplying its top and bottom by the same number. Add the numerators and keep the denominator. Write the answer in lowest terms.
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About this worksheet
Fractions can only be added directly when their pieces are the same size. 1/3 and 1/4 are different-sized pieces, so they are first rewritten in twelfths, a size both can be cut into.
That shared bottom number is the common denominator. Once both fractions use it, add the tops and keep the bottom.
A worked example
1/3 + 1/4 = ?
- Find a number both 3 and 4 divide into: 12.
- Rewrite each fraction: 1/3 = 4/12 and 1/4 = 3/12.
- Add the numerators and keep the denominator: 4/12 + 3/12 = 7/12.
- Check if it simplifies: 7 and 12 share no factor, so 7/12 is in lowest terms.
Answer: 1/3 + 1/4 = 7/12
The common mistake
What it looks like: Adding the tops and adding the bottoms: 1/3 + 1/4 = 2/7.
Why it happens: Adding numerators and denominators separately looks like it follows the rules of adding.
How to fix it: Estimate first: 2/7 is less than 1/3, so it can't be the sum of 1/3 and something more. Pieces have to be the same size before they are added.
Ten minutes a day, on paper. We plan what comes next.
A printed page and a pencil. No screen, no login for your child. Snap a photo when they’re done: AI scores it, and what they missed comes back on the sheets that follow.
- Mon Adding Fractions with Unlike Denominators
- Tue What they missed, back again
- Wed The next step, when they’re ready
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