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3 Addition
and subtraction of
whole numbers
E
3.1 Using a symbol to represent
PL
a missing number or operation
Worked example 1
symbol
Write the missing number.
M
85 + = 200
Always check whether the box represents only one digit or a complete number.
You need to find the difference between 85 and 200.
SA
Method 1: Count on from 85.
+15 +100
85 100 200
Method 2: Subtract 85 from 200.
200 − 85 = 115
Method 3: Use known facts.
85 + 15 = 100 so 85 + 115 = 200
Answer: 85 + 115 = 200
34
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We are working with Cambridge Assessment International Education towards endorsement of this title.
3.1 Using a symbol to represent a missing number or operation
Exercise 3.1
Focus
1 Write the missing number.
37 + = 100
2 Write the missing number so that the scales balance.
E
850 150 300
3
PL
Write the missing digits.
4 + 4 = 100
4 Write the missing number.
M
– 8 = 505
5 Here is a number square with two missing numbers.
The numbers along each edge must add up to 80.
Write the missing numbers.
SA
30 40 10
30
40 20
35
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
We are working with Cambridge Assessment International Education towards endorsement of this title.
3 Addition and subtraction of whole numbers
Practice
6 Write the missing number.
+ 7 + 8 = 28
7 Write the missing number.
− 250 = 1000
E
8 Write the missing number.
48 − = 26
9 PL
The numbers in the two circles add up to the number in the square.
17
12
M
Use the same rule to find these missing numbers.
20 63
SA
100
36
10 Δ and are single digits
Δ+ =4
Write all the possible answers for Δ and
36
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
We are working with Cambridge Assessment International Education towards endorsement of this title.
3.1 Using a symbol to represent a missing number or operation
11 Here are six digit cards.
1 2 3 4 5 6
Use four of the cards to make this calculation correct.
+ = 40
E
Challenge
12 Complete the number sentence.
304 is
PL
more than 296.
13 Break the 4-digit code to open the treasure chest.
65 − 58 =
a
b
41 − 2 = 12
M
c
86 − 79 =
d
67 − 8 = 39
SA
Tip
Code is: Write one
a b c d digit in each
lettered box.
37
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
We are working with Cambridge Assessment International Education towards endorsement of this title.
3 Addition and subtraction of whole numbers
14 Here is a number triangle with some numbers missing. Tip
The numbers along each edge must add up to 90.
Use the numbers 30, 40, 50 and 60 to complete the You could use number
number triangle. counters and move
them around until you
10 find the right answer.
E
PL
15 Here are five number discs.
20
1 2 3 4 5
Use each number once so the total across is the same as the total down.
M
Find different ways.
SA
38
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We are working with Cambridge Assessment International Education towards endorsement of this title.
3.2 Addition and subtraction of whole numbers
3.2 Addition and subtraction of
whole numbers
Worked example 2
Calculate 367 + 185.
E
Estimate:
367 is less than 400 Use any method that
185 is less than 200 you feel you can use
+100
PL
So 367 + 185 is less than 600
Calculate:
+40 +40 +5
quickly and efficiently.
You can use jumps along
a number line starting
from the bigger number.
367 467 507 547 552
3 6 7 Or you can set out the
M
calculation vertically.
+ 1 8 5
Show as much working
4 0 0 300 + 100 as you need.
1 4 0 60 + 80
1 2 7+5
SA
5 5 2
Answer: 552
39
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
We are working with Cambridge Assessment International Education towards endorsement of this title.
3 Addition and subtraction of whole numbers
Worked example 3
Calculate 325 − 58.
Estimate:
325 is 330 to the nearest 10 Use any method that
58 is 60 to the nearest 10 you feel you can use
quickly and efficiently.
330 − 60 = 270
E
Calculate: You can ‘count back’
–60 on a number line. You
can count back 60 and
forward 2 or count back
+2
− 58
325
267
265 PL 267 325 50 and then another 8.
Or you can set out the
calculation vertically.
You will need to
decompose the
200 + 110 + 15 hundreds and tens
− 50 + 8 in 325.
M
200 + 60 + 7 Show as much working
as you need.
Answer: 325 − 58 = 267
SA
compose decompose difference regroup
40
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
We are working with Cambridge Assessment International Education towards endorsement of this title.
3.2 Addition and subtraction of whole numbers
Exercise 3.2
Focus
1 Complete the addition questions.
+20
+3 +1
37 + 24 =
37
E
+40
74 + 38 =
PL 74
–2
M
2 Complete the subtraction questions.
–20
–5
56 – 25 =
SA
56
–20
65 – 19 =
+1 65
41
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We are working with Cambridge Assessment International Education towards endorsement of this title.
3 Addition and subtraction of whole numbers
3 Complete the calculation 749 + 568.
749 = 700 + +
568 = + + 8
+ + 17 =
E
4 Use the most efficient method you can to complete these calculations.
a 102 + 48 b 154 – 140
PL
M
Practice
5 The number in each brick is the sum of the numbers on
SA
the two bricks below it. Tip
60 You will need
to use addition
31 29 and subtraction
to complete
13 18 11
the walls.
18 + 11 = 29
42
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We are working with Cambridge Assessment International Education towards endorsement of this title.
3.2 Addition and subtraction of whole numbers
Complete these number walls.
13 18 23 31 29 17
E
37 48
25 42 28 19
7 8 6
PL
Complete the calculation 786 + 498.
+ 4 9 8
1 4 Add the ones
M
7 Use the most efficient method you can to complete these calculations.
a 543 + 219 b 543 − 219
SA
43
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
We are working with Cambridge Assessment International Education towards endorsement of this title.
3 Addition and subtraction of whole numbers
8 Calculate the difference between 983 and 389.
E
Challenge
9
PL
Circle three numbers that total 750.
50 150 250 350 450
10 Here are four digit cards.
2 4 6 7
M
Use all four cards to make this calculation correct.
+ = 100
SA
11 Circle the number that is closest to 900.
925 891 911 808 950
12 Write the missing digits to complete the calculations.
a b
1 1 5
– 3 4 – 1 5
2 4 4
44
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We are working with Cambridge Assessment International Education towards endorsement of this title.
3.3 Generalising with odd and even numbers
13 Naomi has six number cards.
2 3 4 5 6 7
She makes two 3-digit numbers and adds them together.
a What is the largest total Naomi can make?
E
b
PL
What is the smallest total she can make?
M
3.3 Generalising with odd and
even numbers
SA
Worked example 4
Is it always, sometimes or never true
that when you add two numbers
together you will get an even number?
1 + 2 = 3 which is odd Test some examples by adding two numbers together.
2 + 4 = 6 which is even Try to write a general statement.
Answer: It is sometimes true because when you add two numbers together the
answer may be odd or even.
You are generalising when you look to find a rule.
45
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3 Addition and subtraction of whole numbers
counter-example even generalisation (general statement) odd
Exercise 3.3
Focus
1 Shade all the odd numbers. 416 636 50 32 412
What is the hidden letter?
E
232 861 220 657 154
198 423 8 53 654
PL 110
404
206
5
53
45
851 825 730
676 595 358
294 687 590
682 566 742 174 552
M
2 Work out these calculations:
5 + 11 = 23 + 19 = 101 + 5 =
Each one is the sum of two odd numbers.
SA
Use your answers to help you complete this general statement.
The sum of two odd numbers is always .
3 Here are some statements about odd and even numbers.
Join each calculation to the correct answer.
odd + odd =
even
odd + even =
odd
even + even =
46
Original material © Cambridge University Press 2021. This material is not final and is subject to further changes prior to publication.
