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Adding decimals

decimals

Adding decimals

Line up place values and add tenths and hundredths accurately.

Quick answer

You can add decimals by lining up the decimal points and adding each place value column, just like adding whole numbers.

Learning outcome

By the end of this page, you will be able to add decimals with tenths and hundredths by lining up the decimal points and adding each column correctly. Success signs:

You can write two decimal numbers with the decimal points lined up
You can add tenths and hundredths correctly
You can check your answer makes sense
You can solve real-life problems involving decimal addition

Why this matters

Adding decimals helps you solve problems in everyday life like:

Calculating how much money you have after spending
Measuring ingredients when cooking
Adding up scores in games or sports
Working out distances or weights

In school, you will use this skill when working with money, measurement, and science experiments. It's also important for future maths like percentages and algebra.

How it works

To add decimals, follow these steps:

Write the numbers one above the other, making sure the decimal points are in the same column
Fill in any empty spaces with zeros so both numbers have the same number of digits after the decimal point
Add each column from right to left, just like with whole numbers
Place the decimal point in your answer directly below the decimal points in the numbers

Examples you can see

Let's look at how to add 2.45 and 1.32.

Step	Action	Result
1	Write the numbers with decimal points lined up	2.45 1.32
2	There are no empty spaces to fill	2.45 1.32
3	Add the hundredths column (5 + 2 = 7)	2.45 1.32 -- 0.07
4	Add the tenths column (4 + 3 = 7)	2.45 1.32 -- 0.77
5	Add the units column (2 + 1 = 3)	2.45 1.32 -- 3.77
6	Place the decimal point	2.45 1.32 -- 3.77

Here's another example with 0.8 and 0.25:

Step	Action	Result
1	Write numbers with decimal points lined up	0.80 0.25
2	Fill in the empty space with a zero	0.80 0.25
3	Add hundredths column (0 + 5 = 5)	0.80 0.25 -- 0.05
4	Add tenths column (8 + 2 = 10)	0.80 0.25 -- 1.05
5	Add units column (0 + 0 = 0)	0.80 0.25 -- 0.05
6	Place the decimal point	0.80 0.25 -- 1.05

Try it as a mini adventure

Adventure: The Sweet Shop Challenge You are running a sweet shop and need to add up the prices of different treats for customers. Your first customer buys:

2.45 pounds worth of lollipops
1.32 pounds worth of chocolates

Task: Add these amounts to find the total cost. Step-by-step:

Write the numbers with decimal points lined up
Fill in any missing digits with zeros
Add each column from right to left
Write the answer with the decimal point in the right place

What you'll find: The total cost is 3.77 pounds. Your second customer buys:

0.80 pounds worth of gummy bears
0.25 pounds worth of mints

Task: Add these amounts to find the total cost. What you'll find: The total cost is 1.05 pounds. This adventure helps you understand how adding decimals works in real life.

Common mistakes

Mistake: Not lining up the decimal points correctly
Why it happens: The decimal point is easy to miss or forget
Fix: Always put the decimal points in the same column before adding
Mistake: Forgetting to add zeros in empty columns
Why it happens: Children think it's okay to leave spaces empty
Fix: Add zeros to make sure both numbers have the same number of digits after the decimal point
Mistake: Adding the decimal point in the wrong place in the answer
Why it happens: Confusion about where the decimal point should go
Fix: Always place the decimal point directly under the decimal points in the numbers you're adding
Mistake: Thinking that 0.8 + 0.25 = 0.105
Why it happens: Adding the digits without considering place values
Fix: Remember to add each column separately and carry over when needed

Parent and carer guide

How to help: Use everyday situations to practice adding decimals. For example, when shopping, ask your child to add the prices of items in their basket.
What to say: "Let's line up the decimal points and add the tenths first, then the units."
What not to worry about: It's normal for children to make mistakes at first. Focus on the process, not just getting the right answer.
Practice tips: Make flashcards with decimal addition problems or use online games that focus on decimal addition.
Encouragement: Celebrate small successes. Adding decimals is a skill that takes time to master.

Practice questions

0.45 + 0.32 = ?
Answer: 0.77
1.67 + 2.13 = ?
Answer: 3.80
0.9 + 0.45 = ?
Answer: 1.35
3.21 + 0.79 = ?
Answer: 4.00
0.56 + 0.44 = ?
Answer: 1.00
2.3 + 1.75 = ?
Answer: 4.05
0.85 + 0.15 = ?
Answer: 1.00
4.23 + 0.77 = ?
Answer: 5.00
0.6 + 0.38 = ?
Answer: 0.98
1.25 + 2.75 = ?
Answer: 4.00

FAQ

What is a decimal?
A decimal is a way to write numbers that have parts. For example, 0.5 means 5 tenths, and 0.25 means 25 hundredths.

Why do I need to line up the decimal points?
Lining up the decimal points makes sure you're adding tenths with tenths and hundredths with hundredths. It's like lining up the same types of objects before counting them.

Can I add decimals with different numbers of digits?
Yes! You can add decimals with different numbers of digits. Just add zeros to the shorter decimal to make them the same length.

How do I know if my answer is correct?
Check if your answer makes sense. For example, if you're adding 2.45 and 1.32, your answer should be a bit more than 3. Also, double-check that the decimal point is in the right place.

What happens when I add decimals and get more than 1 in a column?
If you get more than 9 in a column, you carry the extra number to the next column to the left. For example, 7 + 5 = 12, so you write 2 and carry 1 to the next column.