New
New
Year 1

# Furthering understanding of subtraction as decreasing an amount

I can compare subtraction as decreasing an amount to other addition and subtraction structures.

New
New
Year 1

# Furthering understanding of subtraction as decreasing an amount

I can compare subtraction as decreasing an amount to other addition and subtraction structures.

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## Lesson details

### Key learning points

1. Subtraction can be seen as both partitioning and as decreasing an amount.
2. Both types of subtraction stories are represented by the same equation.
3. In an addition story, the amount at the start of the story is increased.
4. In an subtraction story, the amount at the start of the story is decreased.

### Common misconception

After exploring reduction, children may struggle to see partitioning as subtraction because a part is not taken away from the whole.

Make strong links between equations and different subtraction contexts by focusing on what the subtrahend represents in each case.

### Keywords

• Subtraction - To partition one part from another (the subtrahend from the difference), or to decrease an amount by taking an amount away.

• Decrease - Make something smaller in size or quantity decrease.

• Addition - To find the total, or sum, by combining two or more parts (addends), or to increase an amount by adding another.

• Increase - To make something larger/greater in size or quantity.

Encourage children to explain how each subtraction story is represented as an equation, articulating what each part of the equation represents. The inverse relationship between addition and subtraction will be focused upon in depth in a later lesson.
Teacher tip

### 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.
6 - 2 = 4 First, there were 6 apples on the plate. Then, 2 apples were taken off the plate. Now, there are 4 apples on the plate. What does the 2 represent in this story?
The amount left at the end of the story
The amount at the start of the story
Q2.
Which story could match this picture?
Correct answer: First, there were 5 birds. Then, 1 flew off. Now, there are 4 birds.
First, there were 5 birds. Then, 4 flew off. Now, there are 4 birds.
First, there were 4 birds. Then, one flew in. Now, there are 5 birds.
Q3.
Which equation matches this story?
8 - 5 = 3
5 + 3 = 8
Correct answer: 8 - 3 = 5
Q4.
Which equation matches the story?
7 - 3 = 4
Correct answer: 7 - 4 = 3
3 + 4 = 7
Q5.
What is the subtrahend in this problem?
4
5
Q6.
Match the story to the equation it represents.
Correct Answer:8 - 4 = 4,First, there were 8 cars. Then, 4 drove away. Now, there are 4 cars.

First, there were 8 cars. Then, 4 drove away. Now, there are 4 cars.

Correct Answer:5 - 5 = 0,First, there were 5 dogs. Then, 5 ran away. Now, there are 0 dogs.

First, there were 5 dogs. Then, 5 ran away. Now, there are 0 dogs.

Correct Answer:10 - 6 = 4,First, there were 10 birds. Then, 6 flew away. Now, there are 4 birds.

First, there were 10 birds. Then, 6 flew away. Now, there are 4 birds.

## Exit quiz

### 6 Questions

Q1.
A monkey has 7 bananas. She eats 5 of them. How many bananas does she have left?
4
7
Q2.
Which equation matches this 'First, then, now' story?
Correct answer: 6 - 5 = 1
6 - 4 = 2
6 - 1 = 5
Q3.
Write an equation to represent this story.
Correct Answer: 8 - 3 = 5, 8-3=5
Q4.
Is this number line showing an increase or a decrease from the amount at the start of the story?