Addition and subtraction of decimals are essential skills in maths that are used in everyday situations like handling money, measuring distances, or calculating totals. Understanding how to align decimal points and perform accurate calculations properly builds a strong foundation in arithmetic. In this guide, you’ll learn simple methods to add and subtract decimals, along with clear examples to master the addition and subtraction of decimals.

Addition and Subtraction of Decimals
How to Add Decimals
Solved Examples on Addition of Decimals
How to Subtract Decimals
Solved Examples on Subtraction of Decimals
Real-Life Examples of Addition and Subtraction of Decimals
Common Mistakes to Avoid in Addition and Subtraction of Decimals
Conclusion

Addition and Subtraction of Decimals

The addition of decimals means finding the total (sum) of two or more decimal numbers, while the subtraction of decimals means finding the difference between them.
Let us first recall what a decimal is. The number system that has a base of 10 is known as the decimal number. This system extends infinitely in two directions. We can observe that each place on the left side is 10 times larger than the one on its right, and each place on the right side is 10 times smaller than its previous place.

Performing operations like addition and subtraction on decimals is just like whole numbers, but we pay close attention to the decimal point.

Know more about related topics:

How to Add Decimals

Here are the key rules you must always follow to add decimals:

Align the Decimal Points: Write numbers vertically so that decimal points are in a straight line.
Make Decimal Places Equal: If numbers have different decimal lengths, add zeros to make them equal. Example: 4.5 = 4.50. Adding zeros does not change the value.
Perform the Operation: Add the decimal number as you would with whole numbers.
Place the Decimal Point: Bring the decimal point straight down into the answer.

Solved Examples on Addition of Decimals

Example 1: (Like decimals)
Add: 25.36 + 4.256
Solution:
Step 1: Align the decimals.

$%5Cbegin%7Baligned%7D%20%2025.360%20%5C%5C%20%20%2B%5C%2C04.256%20%5C%5C%20%20%5Cend%7Baligned%7D$

Step 2: Add normally
$%5Cbegin%7Baligned%7D%2025.360%5C%5C%20%2B%5C%2C04.256%20%5C%5C%20%5Crule%7B3cm%7D%7B0.4pt%7D%20%5C%5C%2029.616%20%5Cend%7Baligned%7D$

Example 2: (Unlike decimals)
Add: 93.6 + 23.453
Solution: $%20%5Cbegin%7Baligned%7D%2093.360%5C%5C%20%2B%5C%2C23.453%20%5C%5C%20%5Crule%7B2cm%7D%7B0.4pt%7D%20%5C%5C%20117.053%20%5Cend%7Baligned%7D$

How to Subtract Decimals

Here are the key rules you must always follow to subtract decimals:

Align the Decimal Points: Write numbers vertically so that decimal points are in a straight line.
Make Decimal Places Equal: If numbers have different decimal lengths, add zeros to make them equal. Example: 4.5 = 4.50. Adding zeros does not change the value.
Perform the Operation: Subtract the decimal number as you would with whole numbers.
Place the Decimal Point: Bring the decimal point straight down into the answer.

Solved Examples on Subtraction of Decimals

Example 1: (Like decimals)
Subtract: 33.57 − 12.23
Solution:
Step 1: Align the decimals.

$%5Cbegin%7Baligned%7D%20%2033.57%20%5C%5C%20%20-%5C%2C12.23%20%5C%5C%20%20%5Cend%7Baligned%7D$

Step 2: Subtract normally
$%5Cbegin%7Baligned%7D%2033.57%5C%5C%20-%5C%2C12.23%20%5C%5C%20%5Crule%7B2cm%7D%7B0.4pt%7D%20%5C%5C%2021.34%20%5Cend%7Baligned%7D$

Example 2: (Unike decimals)
Subtract: 13.3 − 8.572
Solution: $%5Cbegin%7Baligned%7D%2013.300%5C%5C%20-%5C%2C08.572%20%5C%5C%20%5Crule%7B2cm%7D%7B0.4pt%7D%20%5C%5C%2004.728%20%5Cend%7Baligned%7D$

Real-Life Examples of Addition and Subtraction of Decimals

Addition and subtraction of decimals are used in everyday life more often than you think. From shopping to cooking, understanding how to add and subtract decimals helps you make accurate calculations easily and quickly. Here are a few real-life examples of addition and subtraction of decimals:

Example 1: Nithi has 2 packets of butter that weigh 233.45 g and 175.96 g, respectively. How many grams of butter does she have?
Solution: Weight of first packet = 233.45 g
Weight of second packet = 175.96 g
Total weight of butter = 233.45 + 175.96

$%C2%A0%5Cbegin%7Baligned%7D%20233.45%5C%5C%20%2B%5C%2C175.96%20%5C%5C%20%5Crule%7B3cm%7D%7B0.4pt%7D%20%5C%5C%20409.41%20%5Cend%7Baligned%7D$
Therefore, Nithi has 409.41 g of butter.

Example 2: Sakshi bought a notebook, a pen, and an eraser from a shop. A notebook costs ₹45.75, a pen costs ₹12.50, and an eraser costs ₹5.25. What is the total amount she should pay to the shopkeeper?
Solution: Cost of a notebook = ₹45.75
Cost of a pen = ₹12.50
Cost of an eraser = ₹5.25
Total cost = 45.75 + 12.50 + 5.25
$%5Cbegin%7Baligned%7D%2045.75%20%5C%5C%2B%5C%2C12.50%20%5C%5C%2B%5C%2C05.25%20%5C%5C%20%5Crule%7B2cm%7D%7B0.4pt%7D%20%5C%5C%2063.50%20%5Cend%7Baligned%7D$ Therefore, Sakshi has to pay ₹63.50.

Example 3: Ali studied for 1.5 hours in the morning and 2.25 hours at night. How many hours does he study in total?
Solution: Total study time of Ali = 1.5 + 2.25 hrs
$%5Cbegin%7Baligned%7D%201.50%5C%5C%20%2B%5C%2C2.25%20%5C%5C%20%5Crule%7B2cm%7D%7B0.4pt%7D%20%5C%5C%203.75%20%5Cend%7Baligned%7D$
Therefore, Ali studied for 3.75 hrs.

Example 4: Your account balance is ₹500.75. You spend ₹120.50. What is your remaining balance?
Solution: account balance = ₹500.75
Amount spend = ₹120.50
Remaining balance = ₹500.75 - ₹120.50
$%5Cbegin%7Baligned%7D%20500.75%5C%5C%20-%5C%2C120.50%20%5C%5C%20%5Crule%7B2cm%7D%7B0.4pt%7D%20%5C%5C%20380.25%20%5Cend%7Baligned%7D$

Common Mistakes to Avoid in Addition and Subtraction of Decimals

Not aligning decimal points. Always line them vertically
Forgetting to add zeros. Make decimal places equal
Misplacing the decimal in the answer. Bring it straight down
Treating decimals like whole numbers without alignment. Always consider place value

Conclusion

Addition and subtraction of decimals are practical skills used in daily activities like managing money, measuring ingredients, tracking distances, etc. Learning these skills helps you make better decisions and avoid calculation errors in real life. Understanding how to align decimal points, carefully performing calculations, and regular practice help handle complex problems with confidence, making everyday tasks easier and more accurate.

Frequently Asked Questions on Addition and Subtraction of Decimals

1. What is the most important rule in addition and subtraction of decimals?

Align the decimal points before performing addition or subtraction of decimals.

2. Can we add zeros after decimals?

Yes, adding zeros after does not change the value of the decimal.

3. How to Subtract a Decimal from a Whole Number?

To subtract a decimal number from a whole number, the whole number must first be expressed in decimal form. This is done by placing a decimal point after the whole number and adding zeros as needed so that both numbers have the same number of decimal places. For example, to subtract 3.253 from 7, the number 7 is written as 7.000. This ensures that the digits are properly aligned according to their place values.

4. Can whole numbers be added with decimals?

Yes. Before adding them, convert them into decimal form and then perform the operation.

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Class 7 - Addition and Subtraction of Decimals

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