Align Decimal Points
Place one decimal point directly above the other so matching place values form vertical columns.
Free Interactive Math Tool
Decimal Addition and Subtraction Practice
Align decimal points, add placeholder zeros, regroup when needed, and solve randomized decimal addition and subtraction problems.
Learn How to Line Up Decimal Place Values
Learn why decimal points must align, when to add placeholder zeros, how regrouping works, and how to check whether an answer is reasonable.
Read the Decimal Addition and Subtraction GuideHow It Works
Keep Matching Place Values Together
Decimal points determine where the ones, tenths, hundredths, and thousandths belong. Align the decimal points before calculating so every column contains the same place value.
Add Placeholder Zeros
Write zeros at the end of a decimal when they help create equal-length place-value columns.
Work From Right to Left
Add or subtract each column, carrying or borrowing exactly as you would with whole numbers.
Bring Down the Decimal
Write the answer’s decimal point in the same fixed column as the decimal points above it.
Interactive Practice
Add or Subtract the Decimals
Correct
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Problems
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Decimal Addition
MediumAdd the decimals.
Eighteen and seven tenths plus six and forty-five hundredths.
| Operation | 1,000s | 100s | 10s | 1s | . | 10ths | 100ths | 1000ths |
|---|---|---|---|---|---|---|---|---|
| 1 | 8 | . | 7 | 0 | ||||
| + | 6 | . | 4 | 5 | ||||
| . |
A placeholder zero was added so both numbers show the hundredths place.
Your Response
Complete the answer row.
Starting with the hundredths column, enter one digit in each outlined answer box. The decimal point is already placed for you.
Correct!
You aligned the decimal places and found the correct sum.
Problem
18.70 + 6.45
Answer
25.15
Align the decimal points and write 18.70 + 6.45. Add from right to left and regroup when needed to get 25.15.
Helpful Strategies
Protect the Place Values
Most decimal addition and subtraction errors come from misaligned columns rather than from the arithmetic itself.
Decimal Under Decimal
Use the decimal points as anchors rather than lining up the first or last digits.
Zeros Hold Places
Writing 4.5 as 4.50 does not change its value, but it can make the columns easier to compare.
Regroup by Place Value
Ten thousandths make one hundredth, ten hundredths make one tenth, and ten tenths make one whole.
Estimate to Check
Round the original numbers to nearby whole numbers and compare the estimate with your exact answer.
Understand the Difference
Addition and Subtraction Use the Same Alignment
Combine Decimal Quantities
Add each place-value column from right to left and carry when a column totals ten or more.
12.40 + 3.75 = 16.15
Find the Decimal Difference
Subtract each place-value column from right to left and borrow from the next column when needed.
12.40 − 3.75 = 8.65
Real-World Applications
Where Decimal Operations Appear
Money
Combine prices, calculate change, compare costs, and track account balances to the nearest cent.
Measurement
Add lengths or find differences between measurements recorded in meters, centimeters, or other units.
Science
Combine measured values, compare temperatures, and calculate changes in experimental data.
Statistics and Data
Find totals, differences, and changes among decimal values in tables, graphs, and data sets.
Practice Another Decimal Problem
Generate another problem to practice decimal alignment, placeholder zeros, carrying, borrowing, and estimation.