Adding and subtracting fractions like 2/3 + 1/4
In 5th grade, children learn to add and subtract fractions with different denominators, like 2/3 + 1/4, by first renaming them with the same denominator.
By Robert “Bobby” BarnettMath teacher, parent, and founder of Bobby’s Math Club
Try these with your child
These are real questions from our 5th grade practice. Tap the speaker to hear one read aloud, or the light bulb for a hint, and talk about the answer together.
Question 1 of 3
Which common denominator could you use to add 3/4 and 5/6?
- 10
- 12
- 6
Why this matters
Here your child learns that only same-size pieces can be combined, an idea they will lean on for a long time. It shows up in recipes, measuring wood or fabric, and nearly every fraction word problem from here on, and it is the groundwork for ratios in 6th grade and equations with fractions in middle school. A child who knows this will not write 1/2 + 1/3 = 2/5, a common mistake that can linger for years.
Where kids can get stuck
- Adding the tops and the bottoms, so 1/2 + 1/3 becomes 2/5, which is less than 1/2.
- Changing the denominator but not the numerator, writing 2/3 as 2/12 instead of 8/12.
- Subtracting the smaller fraction from the larger in mixed numbers, so 3 1/4 − 1 1/2 becomes 2 1/4 instead of 1 3/4.
How you can help
- Bake together and combine measurements: if a recipe needs 1/2 cup of sugar and 1/4 cup of brown sugar, ask your child how much sugar that is altogether. Let them show 2/4 + 1/4 = 3/4.
- Fold strips of paper into halves, thirds, fourths, and sixths, and label each piece. Use them to show that 1/2 + 1/3 covers the same length as 5/6.
- Ask a quick estimate question before your child adds: is 1/2 + 3/8 more or less than 1? Talking through benchmarks like 1/2 and 1 helps them catch answers that do not make sense.
Bobby's Math Club offers free practice that grows with your child.
Questions parents ask
Why is my child learning to add fractions with equivalent fractions?
Fractions can only be added when the pieces are the same size, so your child learns to rename them first. Equivalent fractions, like 1/3 and 4/12, describe the same amount cut into different numbers of pieces. Teaching it this way, rather than as a list of steps, helps your child understand why the denominators must match and why you never add them together.
Does my child have to find the least common denominator?
No. Any common denominator works. For 1/2 + 1/3, using sixths is tidiest, but twelfths also give the right answer, 10/12, which equals 5/6. Many teachers accept any common denominator and then ask children to simplify. Using the smallest one keeps numbers easier, and your child will get better at spotting it with practice.
What should my child understand before adding unlike fractions?
It helps if your child can recognize and create equivalent fractions, like knowing 1/2 is the same as 2/4, 3/6, and 4/8. They should also be comfortable adding fractions with the same denominator, such as 3/8 + 2/8 = 5/8. If either feels shaky, revisiting those first often makes unlike denominators click.
Make learning math fun
Bobby's Math Club turns 5th grade math practice into something fun to do together.
- Unlimited free practice
- Practice that starts where your child is and grows with them
- Level-ups, badges, and a cheer for every win
Written by Robert “Bobby” Barnett
Bobby is an award-winning math teacher, the author of Meet Every Learner’s Needs, and the father of two elementary-school math learners. He uses Bobby’s Math Club with his own kids a few times every week. Learn more or contact Bobby.
Ready to watch your child’s confidence grow?
Your 5th grade child can start today with free, unlimited practice that grows with them.
Join the clubNote for teachers: This skill is covered by Common Core math standard 5.NF.A.1: “Add and subtract fractions with unlike denominators (including mixed numbers) by replacing given fractions with equivalent fractions in such a way as to produce an equivalent sum or difference of fractions with like denominators. For example, 2/3 + 5/4 = 8/12 + 15/12 = 23/12. (In general, a/b + c/d = (ad + bc)/bd).” Learn how Bobby's Math Club can help your students grow. (Common Core 5.NF.1)