Common Core Math4th GradeFractions

4.NF.3: Add and Subtract Fractions with Like Denominators

Also written as 4.NF.B.3 and CCSS.MATH.CONTENT.4.NF.B.3 · Cluster: Build fractions from unit fractions.

Make a 4.NF.3 Worksheet All 28 4th Grade Math Standards

The Official Wording

Understand a fraction a/b with a > 1 as a sum of fractions 1/b.

Common Core State Standards, Grade 4, Number & Operations: Fractions · Read it at the source · Checked October 14, 2026

What 4.NF.3 Means in Plain English

Fourth graders see 5/8 as five 1/8 pieces joined (part a) and split it more than one way: 1/8 + 4/8, or 2/8 + 3/8 (part b). They add and subtract mixed numbers like 4 1/3 − 2 2/3, trading a whole for 3/3 when needed (part c).

Part d puts the same moves in word problems, like two trail segments of 1 7/8 and 2 3/8 miles that make 4 2/8 miles in all. Every denominator matches, so the work is counting same-size pieces. Unlike denominators wait for 5th grade (5.NF.1).

4.NF.3 I Can Statements

I can write a fraction like 5/8 as a sum of eighths.
I can add and subtract mixed numbers with the same denominator.
I can solve word problems that join or separate parts of one whole.

4.NF.3 Worked Example

A baking problem where the fourths run out and one whole cup has to be broken into 4/4 before the subtraction works.

Problem

A baker has 3 1/4 cups of flour and uses 1 3/4 cups for a batch of muffins. How much flour is left?

3 1/4 cups of flour, minus 1 3/4 cups

Both amounts are fourths of the same cup, and flour is being taken away, so this is separating parts of one whole.3 1/4 − 1 3/4
There is only 1 fourth, and 3 fourths have to come off. Break one of the 3 wholes into 4 fourths.3 1/4 = 2 + 4/4 + 1/4 = 2 5/4
Now take wholes from wholes and fourths from fourths.2 − 1 = 1, 5/4 − 3/4 = 2/4
Another way to see it: turn both amounts into fourths and subtract the pieces.13/4 − 7/4 = 6/4 = 1 2/4

Answer1 2/4 cups of flour left, which is the same as 1 1/2 cups

Check it: Add it back: 1 2/4 + 1 3/4 = 2 5/4 = 3 1/4 cups, the flour the baker started with.

Common Mistakes with 4.NF.3

Changing the piece size when adding

3/8 + 2/8 = 5/16

Try this: Name the unit out loud: three eighths plus two eighths is five eighths. Adding pieces never changes their size, so the denominator stays 8.

Flipping the fractions to avoid regrouping

3 1/4 − 1 3/4 = 2 2/4, taking the 1 from the 3

Try this: Ask whether there are enough fourths to take away. If not, break one whole into 4/4 first: 3 1/4 becomes 2 5/4.

Losing the whole hidden in a sum

2 3/4 + 1 2/4 = 3 5/4 = 3 1/4

Try this: Circle the 4/4 inside 5/4 and turn it into one whole. Add that whole to the 3, so 3 5/4 = 4 1/4.

Where 4.NF.3 Fits

Comes Before3.NF.1Understand 1/b as one of b equal parts, the unit every sum here is built from.3.NF.2Place fractions on a number line as lengths from 0.

Alongside4.NF.4Multiply a fraction by a whole number, as repeated addition of unit fractions.4.MD.4Add and subtract fractions read off a line plot.

Comes Next5.NF.1Add and subtract fractions and mixed numbers with unlike denominators.5.NF.2Solve word problems with unlike denominators and check them by estimating.

Practice 4.NF.3

Math Worksheet GeneratorFree ToolLike-denominator sums and differences, mixed numbers included, with some problems that need a whole broken apart and an answer key.FractionsLike denominatorsAnswer key

Make a Worksheet

Word Problem GeneratorFree ToolJoin and separate stories in one unit, like cups of flour or miles of trail, for part d.FractionsLike denominatorsGrade 4

Make Word Problems

Quick Check

Write 4/6 as a sum of unit fractions, then as a sum in another way.
1/6 + 1/6 + 1/6 + 1/6, and also 1/6 + 3/6 or 2/6 + 2/6
2 3/5 + 1 4/5
4 2/5 (3 7/5, and 7/5 = 1 2/5)
A ribbon is 5 1/8 feet long. Lia cuts off 2 3/8 feet. How much is left?
2 6/8 feet (4 9/8 − 2 3/8 = 2 6/8)

4.NF.3: Other Names

4.NF.34.NF.B.3CCSS.MATH.CONTENT.4.NF.B.3