Adding and subtracting - what could be simpler? But decimal numbers can cause problems for the unwary! In this KS3 Maths quiz we'll help you get to grips with adding and subtracting decimals.

Decimal numbers contain decimal points, on the left of which are units and on the right tenths, hundredths and thousandths. We use decimal numbers as an alternative to fractions to describe numbers that are smaller than a unit. For example, the fraction ^{1}⁄_{8} could also be written as 0.125. Here we have 1 tenth, 2 hundredths and 5 thousandths. Decimal numbers make addition, subtraction, multiplication and division of fractions much easier. It's just like normal addition and subtraction, except you have to remember to line up the decimal point and add zeros where necessary.

Play this quiz to help familiarise you with adding and subtracting decimal numbers. Plenty of practise and it'll soon become second nature to you.

1.

What is 37.89 + 24.11 - 18.09?

43.91

47.14

48.93

52.25

All the numbers have 2 numbers after the decimal point so there's no need to add any 0s this time

2.

A greyhound runs an average of 37.5mph. A hare runs an average of 44.7mph. How much faster can the hare run?

5.2

6.2

7.2

8.2

44.7 - 37.5 = 7.2. To check you have the correct answer, you can also write 37.5 + 7.2 = 44.7

3.

What is 0.5 + 1.18?

1.23

1.58

1.68

2.32

Remember to use zeros - 0.50

4.

What is 22.7 - 4.13 + 0.008?

17.76

18.441

18.5

18.578

If the numbers are different lengths, remember to line up the decimal points

5.

Mick's test's results for the week are 4.8, 6.6 and 9.4. What is his total?

18.8

20.8

22.8

24.6

4 + 6 + 9 = 19 and 0.8 + 0.6 + 0.4 = 1.8. 1.8 + 19 = 20.8

6.

What is 75.3 - 3.18?

72.12

71.9

71.7

71.2

Remember to put a 0 after 75.3 if you're doing this calculation on paper

7.

What is 783.76 - 2.13?

78.3

76.23

761.15

781.63

Line up the decimal points and use zeros!

8.

A pint of milk costs 76p. However, if you buy 3 pints of milk, you only pay for 2. How much is 3 pints of milk?

76p

£1.52

£2.28

£2.75

76p = £0.76. 0.76 + 0.76 = £1.52

9.

George and Jake pay £4.25 each for a ticket to the circus. How much did they hand over?

£8.25

£8.40

£8.50

£8.75

£4.25 + £4.25

10.

What is 0.5 + 1.8?

2

2.1

2.2

2.3

This is similar to 5 + 18 = 23. Just remember to replace the decimal point!

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