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Maths Adventures

Fairground maths quest: perimeter

A story-led junior maths adventure using rides, tickets and chance games to measure fences, walls and safe zones around places.

Quick answer

Perimeter is the total distance around the edge of a shape. You can find it by adding up all the sides of a shape, like measuring the fence around a playground or the edge of a fairground ride.

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, and you will know how to use this to solve problems about fairground rides, fences, and safe zones. Success signs:
  • You can measure the distance around a shape by counting all the sides
  • You can work out how much fencing you need for a play area
  • You can solve fairground problems using perimeter
  • You can explain why perimeter is useful for keeping people safe

Why this matters

Perimeter is used everywhere, especially in real life. When you're at a fairground, the perimeter helps you know how much space a ride takes up, how much fencing is needed to keep people safe, or how much of a fence you need to go around a fun zone. It's also useful for:
  • Planning how much space you need for a garden or playground
  • Knowing how far you walk around a park
  • Buying the right amount of material to make a fence
  • Designing safe zones around games and rides
In games like Minecraft or Roblox, knowing perimeter helps you build the right-sized walls and fences. In real life, it helps you make smart decisions about space and safety.

How it works

To find the perimeter of any shape, you simply add up all the sides. Here's how to do it step by step:
  1. Look at the shape and count how many sides it has
  2. Measure each side (in metres, feet, or any unit)
  3. Add all the measurements together
  4. Write your answer with the correct unit (like metres or feet)
For example, if a rectangle has sides that are 5m, 3m, 5m, and 3m, you add them all up: 5 + 3 + 5 + 3 = 16 metres

Examples you can see

Let's imagine you're at a fairground and you want to know how much fencing you need for a small play area. Here are some examples: Example 1: Square play area A square play area has 4 equal sides, each 6 metres long. To find the perimeter: 6 + 6 + 6 + 6 = 24 metres So you need 24 metres of fencing. Example 2: Rectangular ride A roller coaster ride has a rectangular shape with sides of 10m, 8m, 10m, and 8m. To find the perimeter: 10 + 8 + 10 + 8 = 36 metres You need 36 metres of fencing around the ride. Example 3: Triangular game booth A triangular game booth has sides of 4m, 5m, and 3m. To find the perimeter: 4 + 5 + 3 = 12 metres You need 12 metres of fencing. Example 4: Circular ride For a circular ride, the perimeter is called the circumference. The formula is C = 2πr, where r is the radius. If the ride has a radius of 5m: C = 2 × 3.14 × 5 = 31.4 metres You need 31.4 metres of safety fence.

Try it as a mini adventure

Adventure: The Fairground Perimeter Quest You are a fairground designer who needs to make sure every ride has the right amount of safety fencing. You have a map with different shapes of rides and game areas. Your mission is to measure and calculate the perimeter of each area to know how much fencing to buy. Task 1: The Ferris Wheel The Ferris wheel has a circular base with a radius of 8 metres. What is the perimeter (circumference) of the base? Answer: 2 × 3.14 × 8 = 50.24 metres Task 2: The Carousel The carousel is a rectangle with sides of 6m, 4m, 6m, and 4m. What is the perimeter? Answer: 6 + 4 + 6 + 4 = 20 metres Task 3: The Maze Game The maze is a square with sides of 5m each. What is the perimeter? Answer: 5 + 5 + 5 + 5 = 20 metres Task 4: The Shooting Gallery The shooting gallery is a triangle with sides of 3m, 4m, and 5m. What is the perimeter? Answer: 3 + 4 + 5 = 12 metres Task 5: The Big Top Tent The big top is a rectangle with sides of 12m, 10m, 12m, and 10m. What is the perimeter? Answer: 12 + 10 + 12 + 10 = 44 metres You've done a great job! You've found how much fencing you need for each area and helped keep everyone safe at the fairground.

Common mistakes

  • Mistake: Forgetting to add all the sides
    Why it happens: Children might only add two sides or skip one side
    Fix: Count the sides carefully and double-check that you've added all of them
  • Mistake: Using the wrong unit of measurement
    Why it happens: Mixing up metres and centimetres
    Fix: Always check what unit is used and keep them consistent
  • Mistake: Confusing perimeter with area
    Why it happens: Both are measurements of shapes, but they're different
    Fix: Remember: perimeter is the distance around, area is the space inside
  • Mistake: Not measuring each side accurately
    Why it happens: Not using a ruler or measuring tape properly
    Fix: Use a ruler or measuring tape and make sure to start from zero

Parent and carer guide

  1. How to help: Encourage your child to draw shapes and measure each side with a ruler
  2. What to say: "Let's measure the sides of your toy box to see how much tape we need for the edge"
  3. How to make it fun: Create a fairground map at home with different shapes and calculate the perimeters
  4. What not to worry about: It's okay if they make a mistake – that's how we learn
  5. Real-life connections: Point out perimeters in your daily life: garden fences, swimming pools, room sizes
  6. Support: Use everyday objects like books, boxes, or toys to practice measuring
  7. Practice: Ask your child to find the perimeter of a room, a table, or a book
  8. Encouragement: Celebrate their efforts and progress, not just correct answers
  9. Visual learning: Use graph paper or shape cutouts to make it hands-on
  10. Repetition: Practice regularly to build confidence and speed

Practice questions

  1. What is the perimeter of a rectangle with sides 7m, 5m, 7m, and 5m?
    Answer: 7 + 5 + 7 + 5 = 24m
  2. What is the perimeter of a square with sides 4m each?
    Answer: 4 + 4 + 4 + 4 = 16m
  3. What is the perimeter of a triangle with sides 3m, 4m, and 5m?
    Answer: 3 + 4 + 5 = 12m
  4. What is the perimeter of a rectangle with sides 10m, 6m, 10m, and 6m?
    Answer: 10 + 6 + 10 + 6 = 32m
  5. What is the perimeter of a square with sides 8m each?
    Answer: 8 + 8 + 8 + 8 = 32m

FAQ

What is perimeter? Perimeter is the total distance around the edge of a shape. You can think of it like walking around the outside of a shape.

How do you find the perimeter of a circle? For a circle, we use the word "circumference" instead of perimeter. It's calculated using the formula C = 2πr, where r is the radius.

Why is perimeter important? Perimeter is important because it helps us know how much space something takes up around the outside. This is useful for fencing, building, and planning safe areas.

Can you find the perimeter of any shape? Yes, you can find the perimeter of any shape by adding up all the sides. Even irregular shapes have perimeters!

How can I practice perimeter at home? You can measure the edges of furniture, draw shapes on paper, or use a measuring tape to find the perimeter of rooms or playgrounds.