# Create Algebraic Expressions to Represent Perimeters and Areas of Shapes

In this worksheet, students will form expressions to represent unknown values of perimeters and areas.

Key stage:  KS 3

Curriculum topic:   Algebra

Curriculum subtopic:   Use and Interpret Algebraic Notation

Difficulty level:

#### Worksheet Overview

In a previous activity, we used letters to represent unknown values and made expressions with them.

For example -  5 pens in a box with n boxes = 5n

This activity looks at other ways you might see this.

You will need your knowledge of area and perimeter of shapes too!

A question could look like this.

Example

Write an expression to represent the perimeter of this triangle.

The perimeter of the triangle is 'all the way round the shape!' we hear you shout!

So, we add up all the sides, which gives us:

## a + b + c

Let's have a look at another example.

Example

Write an expression to represent the area of this rectangle.

The area of the rectangle is 'width x height!'  we hear you shout!

So, we multiply the width by the height, which gives us:

## ab

Now you have the hang of it - let's try some questions!

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