Unit 4 Section 1 : Addition & Subtraction of Decimals

This section will revise some techniques for adding and subtracting whole numbers.
It will also introduce the addition and subtraction of decimal numbers.

Adding and Subtracting with Brackets

With questions which involve brackets, it is important to remember to do the part in brackets first.

Adding and Subtracting Decimals

When adding and subtracting decimal numbers, you need to make sure the decimal points are lined up above each other in the calculation. It also helps if you make both numbers have the same number of decimal places by adding in "0"s at the end of one of the numbers.

 

Exercises

Work out the answers to the questions below and fill in the boxes. Click on the Click this button to see if you are correct button to find out whether you have answered correctly. If you are right then will appear and you should move on to the next question. If appears then your answer is wrong. Click on to clear your original answer and have another go. If you can't work out the right answer then click on Click on this button to see the correct answer to see the answer.

Question 1
Here are some simple additions to get you started:
(a) 3 + 5
(b) 8 + 3
(c) 9 + 7
(d) 14 + 22
(e) 18 + 9
(f) 16 + 15
(g) 47 + 9
(h) 82 + 6
(i) 72 + 17

Question 2
Now work out the answers to these simple subtractions:
(a) 8 - 5
(b) 9 - 7
(c) 7 - 4
(d) 12 - 9
(e) 28 - 15
(f) 48 - 26
(g) 122 - 86
(h) 92 - 47
(i) 57 - 39

Question 3
Indicate whether each of the following statements are true or false.
(a) 3 + 9 = 9 + 3
(b) 3 - 1 = 1 - 3
(c) 8 + 2 + 9 = 9 + 8 + 2
(d) 14 + 7 + 6 = 7 + 20
(e) 3 + 16 - 3 = 16
(f) 17 - 10 = 10 - 17
(g) 4 + 16 + 9 = 11 + 16
(h) 14 + 8 = 8 + 14

Question 4
Work out the answers to these calculations involving brackets.
(a) 3 + (6 - 2)
(b) 5 - (8 - 7)
(c) 15 - (4 + 2)
(d) (17 - 1) - 4
(e) 23 - (4 - 2)
(f) 5 + (14 - 7) - 3
(g) 4 + (71 - 1) + 1
(h) 8 - (3 - 2) + 5
(i) 16 - (8 - 7) - 5

Question 5
Work out the sum of each of the sets of numbers below.

(a) 18 and 15

(b) 6, 10 and 24

(c) 42, 33 and 62

(d) 47, 82 and 37

Question 6
Find the difference between each pair of numbers below.

(a) 18 and 15

(b) 22 and 47

(c) 92 and 46

(d) 57 and 84

Question 7
Miss Sharp teaches 2 classes in one morning. There are 32 children in the first class and 28 in the second.

(a) How many children does she teach altogether?

(b) How many more children are there in the first class than in the second?

Question 8
There are 22 people on a bus.

(a) At the next stop 5 people get off and 12 people get on. How many are now on the bus?

(b) At the next stop nobody gets off and the bus leaves with 35 people on board. How many people got on at this stop?

Question 9
This season Ali has scored 12 goals for his team. Last season he scored 18 goals for his team.

(a) How many goals did he score in total in the two seasons?

(b) What is the difference between the number of goals scored in each season?

Question 10
Jane has 42 CDs. Sarah has 8 fewer than Jane. Nadia has 13 more than Sarah.

How many CDs does Nadia have?

Question 11
In one school there are 3 classes in Year 7. One class has 28 children, one has 29 children and the other has 31 children.

How many children are there in Year 7?

Question 12
Adam has 126 football stickers and Ben has 192. They need 250 stickers each to fill their albums.

(a) How many more stickers does Ben need?

(b) How many more stickers does Adam need?

(c) How many stickers have the boys got in total?

Question 13
There are 216 cars in a car park. In the next hour, 82 cars arrive and 73 cars leave.

How many cars are in the car park at the end of the hour?

Question 14
David buys 3 train tickets that cost 18, 46 and 78.

How much does he spend altogether?

Question 15
Alison goes on holiday on her motorbike. She keeps a record of how far she rides each day.

What is the total distance she rides?
miles

Question 16
Do these questions in your head - try and find a quick method to answer each one.
(a) 18 + 7 + 12
(b) 108 + 19 + 12
(c) 99 + 17 + 11
(d) 17 + 19 + 13
(e) 46 + 23 - 16
(f) 128 - 15 - 13
(g) 72 + 11 + 38
(h) 19 + 6 - 9
(i) 52 + 23 - 12

Question 17
Work out:
(a) 0.3 + 0.6
(b) 0.8 + 0.1
(c) 0.42 + 0.11
(d) 1.2 + 3.7
(e) 1.46 + 3.42
(f) 5.7 + 2.4
(g) 6.7 + 3.6
(h) 5.12 + 8.99
(i) 17.2 + 0.42
(j) 5.6 + 3.21
(k) 0.04 + 1.521
(l) 6.3 + 4.72

Question 18
Work out:
(a) 0.7 - 0.2
(b) 0.9 - 0.6
(c) 1.3 - 0.1
(d) 4.2 - 3.1
(e) 6.9 - 3.5
(f) 8.9 - 7.3
(g) 7.2 - 5.3
(h) 6.6 - 4.8
(i) 19.24 - 8.3
(j) 18.62 - 1.7
(k) 15.2 - 3.46
(l) 11.4 - 3.12


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Produced by A.J.Reynolds January 2001