Adding Decimals (Grade 4)
Adding decimals works just like adding whole numbers, with one key rule: line up the decimal points. This ensures that ones are added to ones, tenths to tenths, and hundredths to hundredths.
Decimal addition is used daily — adding money amounts (₹25.50 + ₹14.75), measuring lengths (3.2 m + 1.8 m), or adding weights (2.5 kg + 1.3 kg).
What is Adding Decimals - Class 4 Maths (Decimals)?
Steps to add decimals:
- Write the numbers vertically, lining up the decimal points.
- Add zeros at the end if the numbers have different decimal places (so they have the same length).
- Add column by column from right to left, just like whole numbers.
- Place the decimal point in the answer directly below the decimal points above.
Line up the decimal points → Add zeros if needed → Add normally → Place the decimal point
Solved Examples
Example 1: Example 1: Adding Tenths
Problem: Find 3.4 + 2.5.
Solution:
Step 1: Line up decimal points:
3.4
+ 2.5
-----
5.9
Answer: 5.9
Example 2: Example 2: Adding with Carrying
Problem: Find 4.7 + 3.8.
Solution:
Step 1: Line up decimal points:
4.7
+ 3.8
-----
8.5
7 tenths + 8 tenths = 15 tenths = 1 one and 5 tenths. Carry 1.
Answer: 8.5
Example 3: Example 3: Adding Hundredths
Problem: Find 5.23 + 3.41.
Solution:
5.23
+ 3.41
------
8.64
Answer: 8.64
Example 4: Example 4: Different Decimal Places
Problem: Find 6.5 + 2.38.
Solution:
Step 1: Write 6.5 as 6.50 (add a zero).
6.50
+ 2.38
------
8.88
Answer: 8.88
Example 5: Example 5: Adding a Decimal and a Whole Number
Problem: Find 12 + 3.75.
Solution:
Step 1: Write 12 as 12.00.
12.00
+ 3.75
------
15.75
Answer: 15.75
Example 6: Example 6: Word Problem — Money
Problem: Aman bought a pen for ₹12.50 and a notebook for ₹35.75. What is the total cost?
Solution:
12.50
+35.75
------
48.25
Answer: The total cost is ₹48.25.
Example 7: Example 7: Word Problem — Length
Problem: A rope is 4.6 m long. Another rope is 3.85 m long. What is their total length?
Solution:
Step 1: Write 4.6 as 4.60.
4.60
+3.85
-----
8.45
Answer: Total length = 8.45 m.
Example 8: Example 8: Adding Three Decimals
Problem: Find 1.2 + 3.45 + 2.3.
Solution:
Step 1: Write as 1.20, 3.45, 2.30.
1.20
3.45
+2.30
-----
6.95
Answer: 6.95
Example 9: Example 9: Word Problem — Weight
Problem: Neha bought 1.5 kg of apples and 2.75 kg of oranges. What is the total weight?
Solution:
1.50
+2.75
-----
4.25
Answer: Total weight = 4.25 kg.
Key Points to Remember
- Always line up the decimal points before adding.
- Add trailing zeros so all numbers have the same number of decimal places.
- Add from right to left, just like whole numbers.
- Carry over when the sum in any column is 10 or more.
- The decimal point in the answer goes directly below the decimal points in the addends.
- Adding a whole number to a decimal: write the whole number with .00.
Practice Problems
- Find 5.3 + 2.9.
- Find 7.25 + 3.48.
- Add 14.6 + 8.35.
- Priya bought vegetables for ₹45.50 and fruits for ₹32.75. What is the total bill?
- A rod is 2.8 m long and another is 1.65 m long. Find their total length.
- Find 6 + 4.52.
- Add: 3.15 + 2.4 + 1.85.
Frequently Asked Questions
Q1. How do you add two decimal numbers?
Write the numbers one below the other, lining up the decimal points. Add trailing zeros if needed so both have the same number of decimal places. Then add column by column from right to left.
Q2. Why must the decimal points be aligned?
Aligning decimal points ensures that digits with the same place value are added together — ones with ones, tenths with tenths, hundredths with hundredths.
Q3. What if one number has more decimal places than the other?
Add trailing zeros to the shorter number. For example, when adding 3.5 and 2.47, write 3.5 as 3.50. Adding zeros after the last decimal digit does not change the value.
Q4. How do you add a whole number and a decimal?
Write the whole number with a decimal point and zeros. For example, 8 becomes 8.00. Then add normally with decimal points aligned.
Q5. Does carrying work the same way in decimal addition?
Yes. If the sum in any column is 10 or more, write the ones digit and carry the tens digit to the next column, just like whole number addition.
Q6. Where is decimal addition used in real life?
It is used in adding money (rupees and paise), measuring lengths, weights, and temperatures, and in billing and shopping calculations.
Q7. Can you add more than two decimals at once?
Yes. Line up all the decimal points, add trailing zeros as needed, and add all columns from right to left. You may need to carry more than once.
Q8. Is adding decimals part of NCERT Class 4?
Yes, addition of decimals (up to two decimal places) is part of the CBSE/NCERT Class 4 curriculum under the Decimals chapter.
