GCSE Maths Number FDP Decimals

Adding decimals

Adding Decimals

Here we will learn about adding decimals including how to solve problems that involve decimal addition.

There are also adding decimals worksheets with word problems and problem solving questions based on Edexcel, AQA and OCR exam questions, along with further guidance on where to go next if you’re still stuck.

What is adding decimals?

Adding decimals involves using column addition to add together decimal numbers by lining up the digits so that they have the same place value.

The ones, decimal points, tenths, hundredths etc. should be lined up. This is particularly important to do if the values we are adding have been given to a different number of decimal places.

E.g.

A similar approach will be used for decimal subtraction.

What is adding decimals?

What is adding decimals?

How to add decimals

In order to add decimals:

  1. Set up a column addition, writing one number above the other. Make sure the decimal points line up to ensure numbers in each column have the correct place value.
  2. Add each column from right to left remembering to carry numbers to the next column when you get a two digit number.
  3. Read off your answer, remembering to include the decimal point.

Explain how to add decimals in 3 steps

Explain how to add decimals in 3 steps

Adding decimals worksheet

Get your free Adding decimals worksheet of 20+ questions and answers. Includes reasoning and applied questions.

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Adding decimals worksheet

Get your free Adding decimals worksheet of 20+ questions and answers. Includes reasoning and applied questions.

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Adding decimals examples

Example 1: adding numbers with one decimal place

Add together 5.8 and 3.7.

  1. Set up a column addition, writing one number above the other. Make sure the decimal points line up to ensure numbers in each column have the correct place value.

2Add each column from right to left remembering to carry numbers to the next column when you get a two digit number.

3Read off your answer, remembering to include the decimal point.

The answer is 9.5.

Example 2: adding numbers with two decimal places

Find the sum of 9.18 and 7.35.

The answer is 16.53.

Example 3: adding numbers with three decimals places

Work out 4.275 + 12.836.

The answer is 17.111.

Example 4: adding whole numbers and decimal numbers

Add together £5 and £2.79.

Fill in missing zeros if it helps.

The answer is £7.79.

Example 5: adding numbers with different amounts of decimal places

Find the sum of 6.4 and 13.701.

Fill in missing zeros if it helps.

The answer is 20.101.

Example 6: adding more than two decimal numbers

Work out 3.79 + 2.184 + 14.6.

Fill in missing zeros if it helps.

The answer is 20.574.

Common misconceptions

  • Not lining up the decimal point

A common error when adding decimals occurs when the decimal points are not lined up but instead the last digits are lined up.

E.g.

Practice adding decimals questions

1. Add together 3.7 and 5.6

9.3
GCSE Quiz True

8.13
GCSE Quiz False

8.3
GCSE Quiz False

9.13
GCSE Quiz False

You must remember to line up the decimal points carefully and carry to the next column if the sum of the digits gives a two digit answer.
 

2. Work out £ 12.84 + £ 6.19

£ 18.103 
GCSE Quiz False

£ 19.03 
GCSE Quiz True

£ 18.913 
GCSE Quiz False

£ 19.3 
GCSE Quiz False

You must remember to line up the decimal points carefully and carry to the next column if the sum of the digits gives a two digit answer.
 

3. Find the sum of 0.069 and 5.987

5.1056
GCSE Quiz False

6.677
GCSE Quiz False

6.56
GCSE Quiz False

6.056
GCSE Quiz True

You must remember to line up the decimal points carefully and carry to the next column if the sum of the digits gives a two digit answer.
 
 

4. Add together 2 and 3.87

5.87
GCSE Quiz True

3.89
GCSE Quiz False

4.07
GCSE Quiz False

23.87
GCSE Quiz False

You must remember to line up the decimal points carefully, you can fill in missing zeros if it helps.
 

5. Find the sum of 9.04 and 17.381

26.421
GCSE Quiz True

18.285
GCSE Quiz False

107.781
GCSE Quiz False

26.385
GCSE Quiz False

You must remember to line up the decimal points carefully and carry to the next column if the sum of the digits gives a two digit answer. You can fill in missing zeros if it helps.
 

6. Work out 20.3 + 13.67 + 0.998

2568
GCSE Quiz False

4.395
GCSE Quiz False

34.968
GCSE Quiz True

34.068
GCSE Quiz False

You must remember to line up the decimal points carefully and carry to the next column if the sum of the digits gives a two digit answer. You can fill in missing zeros if it helps.
 

Adding decimals GCSE questions

1.
 
(a) Work out £ 13.67 + £ 8.59
 
(b) Work out 55.6 + 2.392 + 12.48

 

(3 marks)

Show answer

a)

 

Correct answer of £ 22.26

(1)

b)

 

57.992 or 68.08 or 14.872 seen

(1)

Correct answer of 70.472

(1)

2. Complete the following calculations
 
(a)


 
(b)

 

(5 marks)

Show answer

a)

2 in first box

(1)

7 in second box
 

(1)

b)

8 in top box

(1)

1 in first box in second row

(1)

6 in second box in second row
 

(1)

 

3. Find the perimeter of the irregular pentagon.

(2 marks)

Show answer
4.1+3.5+2.9+4.6+3.8

(1)

Correct answer of 18.9

(1)

Learning checklist

You have now learned how to:

  • Understand and use place value for decimals, measures and integers of any size
  • Use the four operations, including formal written methods, applied to integers, decimals, proper and improper fractions, and mixed numbers, all both positive and negative

The next lessons are

  • Subtracting decimals
  • Multiplying decimals
  • Dividing decimals
  • Ordering decimals

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