5.NF.4: Multiply Fractions
Also written as 5.NF.B.4 and CCSS.MATH.CONTENT.5.NF.B.4 · Cluster: Apply and extend previous understandings of multiplication and division.
The Official Wording
Apply and extend previous understandings of multiplication to multiply a fraction or whole number by a fraction.
Common Core State Standards, Grade 5, Number & Operations: Fractions · Read it at the source · Checked October 14, 2026
What 5.NF.4 Means in Plain English
Fifth graders multiply a fraction by a whole number and by another fraction. 2/3 × 4 means two of the three equal parts of 4, or 8/3. For 2/3 × 4/5 they multiply tops and bottoms to get 8/15, and a 3-by-5 grid shows why.
Part b turns the product into area: a rectangle 2/3 yard by 5/6 yard, tiled with small squares, has an area of 5/9 square yard. 4th graders multiplied fractions only by whole numbers (4.NF.4). Next come scaling (5.NF.5), word problems (5.NF.6) and dividing fractions in 6th grade (6.NS.1).
5.NF.4 I Can Statements
- I can multiply a fraction by a whole number and explain the product.
- I can multiply two fractions and show the product on a grid.
- I can find the area of a rectangle with fraction side lengths.
5.NF.4 Worked Example
One garden bed, measured two ways: tiled with small squares (part b) and multiplied straight across (part a). Both must agree.
A raised garden bed is 2/3 yard wide and 5/6 yard long. What is its area in square yards?
- Area is length times width, so the problem is 2/3 × 5/6. Read it as 2/3 of 5/6: take 5/6 of a yard, cut it into 3 equal parts, keep 2.Area = 2/3 × 5/6
- Tile it. Draw one square yard and cut it into sixths both ways: 36 small squares, each 1/6 yard on a side and 1/36 square yard in area.1 square yard = 36 squares of 1/36
- The bed covers 4 sixths across (that is 2/3) and 5 sixths down. Count the squares: 4 rows of 5.4 × 5 = 20 squares, so 20/36 square yard
- Now multiply the fractions directly: numerators together, denominators together. The grid and the rule must give the same number.2/3 × 5/6 = (2 × 5)/(3 × 6) = 10/18
- Simplify both. 20/36 and 10/18 are the same fraction, 5/9.20/36 = 10/18 = 5/9
Check it: Estimate: both sides are a bit under 1 yard, so the area must be under 1 square yard, and 5/9 is a little over half. Or follow part a as a sequence: 2 × 5/6 = 10/6, then divide by 3 to get 10/18 = 5/9.
Common Mistakes with 5.NF.4
Finding a common denominator first
2/3 × 4/5 = 10/15 × 12/15 = 120/15
Try this: Say it plainly: multiplying needs no common denominator. On a 3-by-5 grid, 2 rows and 4 columns overlap in 8 of 15 squares.
Multiplying the whole number into the bottom too
2/3 × 4 = 8/12
Try this: Write the whole number as a fraction first, 4 = 4/1, so only the top gets the 4: 2/3 × 4/1 = 8/3.
Reading the tiles as wholes
“The bed covers 20 squares, so the area is 20 square yards”
Try this: Label one tile before counting: each small square is 1/6 by 1/6, which is 1/36 of a square yard, so 20 tiles make 20/36.
Where 5.NF.4 Fits
Practice 5.NF.4
Quick Check
- 2/3 × 4
- 3/4 × 2/5
- A rug is 1/2 yard by 3/4 yard. What is its area?