5.NBT.7: Add, Subtract, Multiply and Divide Decimals
Also written as 5.NBT.B.7 and CCSS.MATH.CONTENT.5.NBT.B.7 · Cluster: Perform operations with multi-digit whole numbers and with decimals to hundredths.
The Official Wording
Add, subtract, multiply, and divide decimals to hundredths, using concrete models or drawings and strategies based on place value, properties of operations, and/or the relationship between addition and subtraction; relate the strategy to a written method and explain the reasoning used.
Common Core State Standards, Grade 5, Number & Operations in Base Ten · Read it at the source · Checked October 14, 2026
What 5.NBT.7 Means in Plain English
Fifth graders work all four operations on decimals to hundredths and explain where the decimal point lands. For 2.4 × 1.5 they reason that 24 tenths × 15 tenths is 360 hundredths, or 3.6. And 7.2 ÷ 0.8 asks how many 8 tenths fit in 72 tenths: 9.
Models and place-value reasoning come first, with the written method connected to them, so a student can say why 3.6 is right rather than count decimal places by rule. Fluent decimal algorithms arrive in 6th grade (6.NS.3), and the estimating habit from 5.NBT.4 catches a misplaced point.
5.NBT.7 I Can Statements
- I can add and subtract decimals by lining up the places.
- I can multiply decimals and explain where the decimal point goes.
- I can divide a decimal by reasoning about tenths and hundredths.
5.NBT.7 Worked Example
A decimal product worked by renaming both factors as tenths, so the decimal point is placed by reasoning rather than by rule.
A ribbon is 2.4 meters long. How long are 1.5 of those ribbons? Find 2.4 × 1.5 and explain where the decimal point goes.
- Estimate: 1.5 ribbons is more than one ribbon and less than two, so the answer is between 2.4 and 4.8.2.4 < 2.4 × 1.5 < 4.8
- Rename both as tenths so they are whole numbers: 2.4 is 24 tenths, 1.5 is 15 tenths.24 tenths × 15 tenths
- Multiply the whole numbers with the algorithm from 5.NBT.5.24 × 15 = 360
- Now the unit. A tenth times a tenth is a hundredth (1/10 × 1/10 = 1/100), so the 360 is 360 hundredths.360 hundredths = 3.60
- Write it as a decimal and compare with the estimate: 3.6 sits between 2.4 and 4.8.2.4 × 1.5 = 3.6
Check it: Break 1.5 into 1 + 0.5: one ribbon is 2.4 and half a ribbon is 1.2, so 2.4 + 1.2 = 3.6. The written method and the model agree.
Common Mistakes with 5.NBT.7
Lining up the right edge instead of the decimal point
3.5 + 0.25 written with the 5s aligned, giving 0.60 or 6.0
Try this: Write 3.5 as 3.50 so both numbers have hundredths, then line up the decimal points: 3.50 + 0.25 = 3.75.
Placing the point by copying the factors
2.4 × 1.5 = 36.0 or 0.36
Try this: Estimate before multiplying: 2.4 × 1.5 is between 2.4 and 4.8, so only 3.6 fits. Then explain it as tenths times tenths.
Expecting division by a decimal to make things smaller
7.2 ÷ 0.8 = 0.9 because “dividing makes it smaller”
Try this: Ask the question the division poses: how many 0.8s are in 7.2? Count by 0.8 on a number line to reach 7.2 in 9 jumps.
Where 5.NBT.7 Fits
Practice 5.NBT.7
Quick Check
- 4.35 + 2.8
- 6 − 2.47
- Nine pencils cost $4.05. How much does one pencil cost?