Worked example 1
Add 3.47 + 12.6.
Write 12.6 as 12.60 to match decimal places. Stack and add: 3.47 + 12.60 = 16.07. The decimal point comes straight down.
Answer: 16.07
Grade 6 Math · Topic 19
Adding and Subtracting Decimals
Adding and subtracting decimals works just like with whole numbers — with one rule: line up the decimal points. Fill in zeros if one number has fewer decimal places so the digits line up. Then add or subtract column by column, carrying or borrowing as usual.
Lesson alignment: 6.NS.B.3 · Take your time. You can return to this lesson whenever you need it.
Explore visually
Line up decimal points to add or subtract
Place each digit in its matching column. Add zeros at the end when a place is empty; then follow the carry or regrouping row.
Think first: Before opening the model, predict which column will carry when you add 3.47 + 12.6.
Ready? Reveal the model and try your prediction
Swipe horizontally to see the full diagram.
Turn on JavaScript to adjust this model. The examples and practice below work without it.
Follow the worked examples
Read each step, then cover the explanation and see if you can explain why it works.
Worked example 2
Subtract 20 - 6.385.
Write 20 as 20.000. Subtract column by column with borrowing: 20.000 - 6.385 = 13.615.
Answer: 13.615
Try a few on your own
Work these on paper first. Open “Check” when you are ready to compare your answer.
- 4.2 + 3.75 =
Check
7.95
- 8.06 + 1.4 =
Check
9.46
- 15.3 + 2.78 =
Check
18.08
- 6.085 + 9.5 =
Check
15.585
- 12.6 - 4.32 =
Check
8.28
- 20 - 8.7 =
Check
11.3
- 50.05 - 17.6 =
Check
32.45
- 100 - 23.45 =
Check
76.55
Try this situation 1
Liam buys a notebook for $3.49 and a pen for $1.75. How much does he spend in total?
Show a worked solution
Answer: $5.24.
Start by writing the calculation clearly: 3.49 + 1.75 = 5.24. Decimal points line up, then add.
Try this situation 2
A water tank held 50 liters. After watering plants, 36.85 liters are left. How much was used?
Show a worked solution
Answer: 13.15 liters.
Start by writing the calculation clearly: 50.00 - 36.85 = 13.15.
Fresh questions · saved on this device
Practice this skill
Try a fresh set each time. Answer one question, check your thinking, and read the explanation. If you miss one, return to the visual model and try another round.
Question 1 of 50 correct so far
Session complete
Check what you learned
Answer these five questions on your own. You can review the explanations after you submit and try again whenever you like. This short check is for practice, not a grade.
Practice and finish
Try the linked topic quiz for more practice. If something is tricky, return to the example and look for the step that changes the numbers or representation.
Your checkmark, skill-practice sessions, and best exit-check score are saved on this browser and device. The course page can download a progress report to share with a tutor or teacher.
More Grade 6 resources
Use these free materials if you want another explanation, extra paper practice, or a broader review.