Superhero maths quest: perimeter

Quick answer

Perimeter is the total distance around the edge of a shape. You can find it by adding up all the sides.

Learning outcome

By the end of this page, you will be able to measure the perimeter of any shape by adding up all the sides, like a superhero measuring safe zones and rescue routes.

• You can identify all the sides of a shape
• You can add up all the sides to find the perimeter
• You can measure and calculate the perimeter of rectangles and other shapes
• You can use perimeter to solve real-world problems like planning safe zones

Why this matters

Perimeter is like a superhero’s superpower to measure how far around something is! When you're a superhero, you need to know how much fencing is needed to protect a city, or how far you need to run to complete a rescue mission. In real life, perimeter helps you plan gardens, work out how much rope you need, or even decide how far you can walk around a park.

How it works

Perimeter means "the distance around the edge of a shape." To find the perimeter:

1. Look at all the sides of the shape
2. Measure each side (if needed)
3. Add up all the sides

It's like walking around the outside of a shape and counting how many steps you take. For example, if a rectangle has sides that are 5 metres and 3 metres, you add them all up to find the perimeter.

Examples you can see

Imagine you're a superhero with a special power to measure distances. Let’s look at a few shapes:

Rectangle

A rectangle has 4 sides. If one side is 6 metres and the opposite side is also 6 metres, and the other two sides are 4 metres each, you add them all together:

6 + 4 + 6 + 4 = 20 metres

The perimeter is 20 metres.

Square

A square has 4 equal sides. If each side is 5 metres:

5 + 5 + 5 + 5 = 20 metres

The perimeter is 20 metres.

Triangle

A triangle has 3 sides. If each side is 7 metres:

7 + 7 + 7 = 21 metres

The perimeter is 21 metres.

Irregular Shape

Some shapes don’t have equal sides. Let’s say a shape has sides of 3, 4, 5, 6, and 7 metres:

3 + 4 + 5 + 6 + 7 = 25 metres

The perimeter is 25 metres.

Try it as a mini adventure

Join Captain Perimeter on a superhero mission to protect the city! You have a map of the city, and your job is to find the perimeter of safe zones to help plan where to place the city’s new protective fence.

Step 1: Look at the city map. You see a rectangular safe zone with sides of 10 metres, 8 metres, 10 metres, and 8 metres.

Step 2: Add up all the sides to find the perimeter.

Step 3: Decide how much fencing you need to build around the zone.

Now it’s your turn! You are a superhero with a mission to find the perimeter of a shape on the map. Here’s your challenge:

1. Find the perimeter of a square with sides of 9 metres
2. Find the perimeter of a triangle with sides of 6, 8, and 10 metres
3. Find the perimeter of a shape with sides of 5, 5, 3, 3, and 7 metres

Common mistakes

• Mistake: Forgetting to add up all the sides
• Why it happens: Superheroes get excited and forget to count carefully!
• Fix: Make sure to count every side and write them down before adding.

• Mistake: Adding the same side twice
• Why it happens: It's easy to confuse the sides when shapes look similar.
• Fix: Label each side clearly or use a ruler to measure each one once.

• Mistake: Not using the right units
• Why it happens: Sometimes kids forget that perimeter is measured in units like metres or centimetres.
• Fix: Always write the units after your answer, like "20 metres".

Parent and carer guide

Help your child understand perimeter by using everyday objects. For example:

• Draw a rectangle on the floor with tape and ask your child to walk around it to measure the perimeter
• Use a ruler to measure the sides of a book or a box and add them up
• Play a game where you measure different rooms in your house and add up the walls

Ask questions like:

• How many sides does this shape have?
• Can you add up all the sides to find the perimeter?
• What unit should we use for measuring this shape?

Remember to be patient and encourage your child to count carefully. Mistakes are part of learning, so celebrate every correct answer!

Practice questions

1. Find the perimeter of a rectangle with sides of 7 metres and 5 metres
2. Find the perimeter of a square with sides of 6 metres
3. Find the perimeter of a triangle with sides of 4, 5, and 6 metres
4. Find the perimeter of a shape with sides of 3, 3, 4, 4, and 5 metres
5. Find the perimeter of a rectangle with sides of 10 metres and 8 metres

Answers:

1. 7 + 5 + 7 + 5 = 24 metres
2. 6 + 6 + 6 + 6 = 24 metres
3. 4 + 5 + 6 = 15 metres
4. 3 + 3 + 4 + 4 + 5 = 19 metres
5. 10 + 8 + 10 + 8 = 36 metres

FAQ

What is perimeter?

Perimeter is the total distance around the edge of a shape. You can find it by adding up all the sides of the shape.

How do I find the perimeter of a square?

A square has 4 equal sides. To find the perimeter, you add all four sides together. If one side is 5 metres, then 5 + 5 + 5 + 5 = 20 metres.

Can I find the perimeter of any shape?

Yes! As long as you can see all the sides of a shape, you can add them up to find the perimeter. Even shapes with different side lengths can have their perimeter calculated this way.

Why do I need to know perimeter?

Knowing perimeter helps you solve real-world problems like planning how much fencing you need, how far you can run around a park, or how much material you need to make a border.

What if I can’t measure the sides?

If you can't measure the sides, you can still add up the sides if they are given to you. For example, if a triangle has sides of 3, 4, and 5 units, you add 3 + 4 + 5 = 12 units.