# Solve problems involving comparison and change

I can solve problems involving comparison and change deciding when to use multiplication or division.

# Solve problems involving comparison and change

I can solve problems involving comparison and change deciding when to use multiplication or division.

## Slide deck

## Lesson details

### Key learning points

- A change in length can be described using multiplication or division.
- Comparison and change problems can be represented visually to support understanding.
- To find ___ times a length, we know we will be multiplying the length by ___.
- To find a unit fraction times a length, divide the length into the number of equal parts represented by the denominator.

### Common misconception

Children may say 'ten times shorter' which is imprecise. Children are more familiar with multiplication resulting in an increase, and need to appreciate that it can also result in a decrease.

We say, 'ten times the original height' because this is more precise especially when the scale factor is fractional. When we multiply by a unit fraction, it is the same as dividing the whole by the denominator. This results in a decrease in length.

### Keywords

Comparison - When a comparison is made, we are determining how different two objects are. In this case, how many times longer, taller or deeper an object is than another.

Change - A comparison can also be made between an object before, and then after, a change. Examples of a change include a change in height of a flower due to growth.

Unit fraction - A unit fraction is a fraction where the numerator is one.

### 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).

## Video

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## Worksheet

## Starter quiz

### 6 Questions

The tree is 50 m tall -

The car is 10 m tall

The tree is 5 m tall -

The car is 1 m tall

The tree is 500 cm -

The car is 100 cm tall

The tree is 50 cm tall -

The car is 10 cm tall

## Exit quiz

### 6 Questions

400 m x $${1}\over{4}$$ -

0.4 km ÷ 4

4 km x $${1}\over{4}$$ -

4,000 m ÷ 4

400 cm x $${1}\over{4}$$ -

4 m ÷ 4

4 m x $${1}\over{4}$$ -

400 cm ÷ 4