New
New
Year 3

# Use the additive relationship to rearrange and solve equations

I can use the additive relationship to rearrange and solve equations.

New
New
Year 3

# Use the additive relationship to rearrange and solve equations

I can use the additive relationship to rearrange and solve equations.

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## Lesson details

### Key learning points

1. When a whole is missing, add the parts together.
2. To find a missing part, subtract the other part from the whole.
3. Rearrange the equation to make it easier to calculate the missing number.

### Common misconception

Pupils may use the wrong operation to find missing numbers, adding when they should be subtracting or vice versa.

Encourage pupils to draw bar models, focusing on the whole in the problem. They should also write problems, understanding where the missing number is and rearranging equations so that they can calculate the answers.

### Keywords

• Equation - An equation shows that one number or calculation is equal to another.

• Rearrange - Rearrange means to change an equation. It could mean moving the parts or the whole or changing it from an addition into a subtraction equation.

### Licence

This content is © Oak National Academy Limited (2024), licensed on Open Government Licence version 3.0 except where otherwise stated. See Oak's terms & conditions (Collection 2).

## Starter quiz

### 6 Questions

Q1.
Which number in this equation is the sum? 18 + 8 = 26
8
18
Q2.
Which number is this equation is the minuend? 43 − 10 = 33
33
10
Q3.
Calculate the missing number in this equation: − 14 = 10
Q4.
Calculate the missing number in this equation: 35 − = 25
Q5.
What is the difference between 40 and 140?
Q6.
Calculate the missing number in this equation: = 71 − 11

## Exit quiz

### 6 Questions

Q1.
Which of these are equations?
Correct answer: 24 + 10 = 34
Correct answer: 96 − 20 = 76
5 + 5 + 10
Correct answer: 10 + 5 = 5 + 10
Q2.
The equation 16 + 20 = 36 has been rearranged in different ways. Match up the parts of the equations to make them correct.
Correct Answer:20 = ,36 − 16

36 − 16

Correct Answer:36 = ,20 + 16

20 + 16

Correct Answer:16 = ,36 − 20

36 − 20

Q3.
Find the missing part. 20 + \$\$\square\$\$ = 110
70
80
100
Q4.
What is the missing number? 65 = \$\$\square\$\$ − 30
Q5.
There are some cherries in a bowl. Polly eats 12 cherries. There are 21 left. How many cherries were in the bowl to start with?
9
23
Q6.
There are 45 cherries in a bowl. Petra eats some cherries. There are 15 left. How many cherries did Petra eat?