Adding and Subtracting Decimals Examples in Math

Start with the recap, study the fully worked examples, then use the practice problems to check your understanding of Adding and Subtracting Decimals.

This page combines explanation, solved examples, and follow-up practice so you can move from recognition to confident problem-solving in Math.

Concept Recap

Adding and subtracting numbers with decimal points by aligning the decimal points vertically so that digits with the same place value line up.

Think of money: $3.75+$2.50\$3.75 + \$2.50. You line up the dollars with dollars, the dimes with dimes, and the pennies with pennies. The decimal point is the anchor that keeps everything in the right place.

Read the full concept explanation →

How to Use These Examples

  • Read the first worked example with the solution open so the structure is clear.
  • Try the practice problems before revealing each solution.
  • Use the related concepts and background knowledge badges if you feel stuck.

What to Focus On

Core idea: Adding and subtracting decimals is place-value column work where the decimal points are stacked so tenths meet tenths and hundredths meet hundredths.

Common stuck point: The procedure for adding and subtracting decimals is the easy part; the trap is right-justifying digits instead of aligning points. Asking "Do the numbers have decimal points I must line up before adding or subtracting?" first is what keeps a correct-looking calculation from being attached to the wrong concept.

Sense of Study hint: Ask: Do the numbers have decimal points I must line up before adding or subtracting?

Worked Examples

Example 1

easy
Calculate 3.4+2.73.4 + 2.7.

Answer

6.1

First step

1
Line up the decimal points:

Full solution

  1. 2
    3.4
  2. 3
    + 2.7
  3. 4
    Tenths: 4+7=114+7=11, write 1, carry 1.
  4. 5
    Ones: 3+2+1=63+2+1=6.
  5. 6
    Result: 6.1.
Always align decimal points before adding. Then add as with whole numbers, keeping the decimal point in the same position.

Example 2

medium
A ribbon is 5.60 meters long. You cut off 2.35 meters. How much ribbon is left?

Example 3

medium
Calculate 14.75−8.093+2.414.75 - 8.093 + 2.4.

Example 4

easy
A pencil costs \$0.75 and an eraser costs \$0.40. How much for both?

Example 5

medium
Jamie has \$10.00. She spends \$3.45 on lunch and \$2.20 on a snack. How much is left?

Example 6

hard
A jar holds 1.51.5 L. You add 0.3750.375 L, then pour out 0.60.6 L. How much is in the jar?

Practice Problems

Try these problems on your own first, then open the solution to compare your method.

Example 1

easy
Calculate 1.8+0.51.8 + 0.5.

Example 2

medium
A pitcher has 2.75 liters of juice. After pouring 1.40 liters, how much is left?

Example 3

easy
Add: 0.3+0.40.3 + 0.4.

Example 4

easy
Add: 1.5+2.31.5 + 2.3.

Example 5

easy
Subtract: 0.8−0.50.8 - 0.5.

Example 6

easy
Add: 2.50+1.252.50 + 1.25.

Example 7

easy
Subtract: 5.7−2.45.7 - 2.4.

Example 8

easy
Add: 0.25+0.250.25 + 0.25.

Example 9

easy
Subtract: 1.00−0.401.00 - 0.40.

Example 10

easy
Add: 3.6+0.43.6 + 0.4.

Example 11

medium
Add: 3.5+2.753.5 + 2.75.

Example 12

medium
Subtract: 6.2−1.456.2 - 1.45.

Example 13

medium
Add: 12.8+7.95+0.312.8 + 7.95 + 0.3.

Example 14

medium
Subtract: 10−3.6510 - 3.65.

Example 15

medium
A runner does 2.42.4 km, then 1.851.85 km, then 3.53.5 km. Total distance?

Example 16

medium
Find the missing addend: 4.6+□=9.14.6 + \square = 9.1.

Example 17

medium
Subtract: 7.03−2.87.03 - 2.8.

Example 18

medium
Add: 0.07+0.9+0.1230.07 + 0.9 + 0.123.

Example 19

medium
Subtract: 20.4−6.8520.4 - 6.85.

Example 20

challenge
Evaluate 5−2.3+0.45−1.75 - 2.3 + 0.45 - 1.7 left to right.

Example 21

challenge
A jug holds 2.52.5 L. You pour out 0.850.85 L, then add 1.21.2 L, then pour out 0.60.6 L. How much is in the jug?

Example 22

challenge
Two numbers add to 10.010.0. One is 3.853.85 larger than the other. Find both numbers.

Example 23

easy
Add: 2.1+3.62.1 + 3.6.

Example 24

easy
Subtract: 9.4−5.29.4 - 5.2.

Example 25

easy
Add: 4.5+1.54.5 + 1.5.

Example 26

easy
Subtract: 4.0−1.64.0 - 1.6.

Example 27

medium
Add: 4.7+2.854.7 + 2.85.

Example 28

medium
Subtract: 8.3−4.758.3 - 4.75.

Example 29

medium
Add: 0.125+0.50.125 + 0.5.

Example 30

medium
Subtract: 15−6.3215 - 6.32.

Example 31

medium
Find the missing addend: □+3.45=8.0\square + 3.45 = 8.0.

Example 32

medium
Add: 1.05+2.5+0.751.05 + 2.5 + 0.75.

Example 33

medium
Subtract: 7.005−2.47.005 - 2.4.

Example 34

medium
A board is 3.63.6 m. You saw off 0.850.85 m, then attach 1.21.2 m. How long is it now?

Example 35

medium
Subtract: 25.05−9.825.05 - 9.8.

Example 36

hard
Add: 0.999+0.1110.999 + 0.111.

Example 37

hard
Subtract: 1−0.0011 - 0.001.

Example 38

hard
Evaluate: 6.4−2.85+0.15−1.76.4 - 2.85 + 0.15 - 1.7.

Example 39

hard
Find the missing addend: □+4.36=10.005\square + 4.36 = 10.005.

Example 40

challenge
Two numbers add to 7.57.5. One is 1.251.25 smaller than the other. Find both.

Example 41

challenge
A grocer's receipt totals \$24.85. Three items cost \$5.99, \$8.49, and \$4.10. Find the cost of the fourth item.
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Background Knowledge

These ideas may be useful before you work through the harder examples.

additionsubtractionplace valuedecimals