Summarize this article:
Last updated on 11 September 2025
Addition and subtraction are two commonly used arithmetic operations for all numbers, including decimals. The addition or subtraction of decimal numbers should ensure that decimal points are correctly aligned. Learning to solve decimals helps us determine precise measurements and calculate averages or percentages. This topic will help you learn how to add and subtract decimal numbers easily.
Addition of decimals is the process of finding the sum of numbers that contain decimal points. Subtraction of decimals is the process of finding the difference between such numbers.
In these methods, check whether the numbers have the same number of digits after the decimal point (i.e., are "like decimals"). If not, add trailing zeros to make them like decimals. If not, convert the unlike terms to like terms by adding additional zeroes after the decimal point.
As we have learned, decimal numbers can be classified as like or unlike. To find the sum of two decimals, we need to apply the following steps:
1. Check whether the decimal points are vertically aligned.
2. If necessary, add trailing zeros to make the numbers have the same number of digits after the decimal point.
3. Add as whole numbers, then place the decimal point in the result directly under the other decimal points.
Unlike decimals, values always have a different number of digits after the decimal point.
They can be easily converted to like decimals by adding extra zeroes after the decimal point. Note that adding extra zeros does not change the value of the number.
Add 10.22 and 3.5
Step 1: Here, the given decimal values are not aligned correctly, so they are unlike.
10.22
+ 3.5
Step 2: To make them alike, we add extra zeroes as shown below:
10.22
+ 3.50
Step 3: We now add the values to find the sum.
10.22
+ 3.50
13.72
Since the like decimals have the same number of digits after the decimal point, they can be aligned correctly and added just like whole numbers. The decimal point must be placed accurately in the final result.
Example: Add 95.7 and 82.3
95. 70
+ 82. 30
178.00
To find the difference between two decimals, we use the following steps:
The subtraction of like numbers is calculated in the same way as whole numbers, by subtracting the smaller number from the larger one.
Subtract 40.32 from 98.25
98.25
- 40.32
57.93
To subtract unlike decimals, first, add extra zeroes to the shorter decimal.
Then, subtract the numbers in the same way as, like decimals.
Subtract 20.486 from 78.6
78.600
- 20.486
58.114
Decimals are significant components of mathematics. They are widely used in real-life scenarios beyond math, where the precision of numbers matters. Here are a few real-life applications of addition and subtraction of decimals:
Students often make mistakes while working with decimal numbers. Let us see some common mistakes and how to avoid them in addition and subtraction of decimals:
Add 30.67 and 15.3
45.97
We need to convert the unlike decimals by adding a zero: 15.3 to 15.30. Then add the numbers: Then present aligned code block.
30.67
+ 15.30
45.97
Amy buys clothes from a store. She buys: Shirts for $333.65 Pants for $400.50 How much does she need to pay in total?
The total amount to be paid is $734.15.
To find the total amount to be paid, we add up the prices of shirts and pants:
333.65
+ 400.50
734.15
Therefore, the total amount to be paid is $734.15. Replace the $734.14 instance with $734.15. (Also format the items as separate lines: Shirts — $333.65 and pants — $400.50).
Jake has $520.00 in his wallet. He buys a miniature car for $382.75. How much money does he have left?
The money left is $137.25.
Here, to find the amount left, we subtract the amount spent from his initial amount.
520.00
– 382.75
137.25
Therefore, the money left is $137.25.
Tom weighed 48.5 kg last month. He now weighs 75.8 kg. How much weight did he gain?
Tom gained 27.3 kg.
Here, we find the difference between his current weight and the weight he had.
75.8
- 48.5
27.3
Therefore, the weight Tom gained is 27.3 kg.
Carl's car consumes 4.25 liters of fuel on Monday and 3.9 liters on Tuesday. How much fuel did he use in total?
The total fuel used is 8.15 liters.
To find the total fuel consumption, add the fuel consumption on Monday and Tuesday.
Convert 3.9 to 3.90 and add:
4.25
+ 3.90
8.15
Therefore, Carl used 8.15 liters of fuel in total.