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Maths Adventures

Robot maths quest: perimeter

A story-led junior maths adventure using circuits, commands and machine logic to measure fences, walls and safe zones around places.

Quick answer

Perimeter is the total distance around the edge of a shape. You measure perimeter 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 counting all the sides and adding them together. Success signs:
  • You can identify all the sides of a shape
  • You can add up all the sides to find the total distance
  • You can measure shapes in your home or outside
  • You can help a robot measure safe zones and fences

Why this matters

Perimeter is important for many real-world jobs and situations. If you're building a fence, you need to know how much fencing you'll need. If you're planning a robot's path, you need to know how far it must travel around a shape. When you're designing a garden, you might want to know how much edging you need. Even in games and stories, robots need to know how far to move around obstacles or safe zones.

How it works

To find the perimeter of a shape, you need to:
  1. Look at all the sides of the shape
  2. Measure each side
  3. Add all the measurements together
The perimeter is like walking around the outside of a shape and counting how many steps you take in total. You don't count the inside, just the edge.

Examples you can see

Let's imagine you're helping a robot build a safe zone. The robot needs to know how far it must travel around the edge of a shape to keep itself safe. Example 1: Rectangle Imagine a rectangle that is 5 metres long and 3 metres wide.
  • Two sides are 5 metres long
  • Two sides are 3 metres long
  • Perimeter = 5 + 5 + 3 + 3 = 16 metres
Example 2: Square A square with sides that are all 4 metres long.
  • Four sides are 4 metres long
  • Perimeter = 4 + 4 + 4 + 4 = 16 metres
Example 3: Triangle A triangle with sides of 6, 8, and 10 metres.
  • Perimeter = 6 + 8 + 10 = 24 metres

Try it as a mini adventure

Robot Maths Quest: The Safe Zone Challenge You are a robot programmer helping build a safe zone for a robot. The safe zone is a rectangle that is 7 metres long and 4 metres wide. You need to help the robot know how far it must walk around the outside to stay safe. Step 1: The robot needs to walk along the long side of 7 metres. Step 2: Then it walks along the wide side of 4 metres. Step 3: Then it walks along the long side again (7 metres). Step 4: Finally, it walks along the wide side again (4 metres). How far did the robot walk? Add up all the sides: 7 + 4 + 7 + 4 = 22 metres The robot must walk 22 metres around the outside of the safe zone. Now try this challenge:
  • Draw a rectangle that is 6 metres long and 3 metres wide
  • Measure each side
  • Add all the sides together
  • How many metres did you walk around the outside?

Common mistakes

  • Mistake: Forgetting to measure all sides Why it happens: The robot might only measure two sides and forget the other two. Fix: Always count all the sides of the shape. You can trace your finger around the outside to make sure you don't miss any.
  • Mistake: Adding the inside measurements instead of the outside Why it happens: A child might measure the inside of a shape, like the length of a garden bed, instead of the edge. Fix: Remember, perimeter is always the distance around the outside edge.
  • Mistake: Not using the same units Why it happens: One side might be measured in metres and another in centimetres. Fix: Always use the same unit for all measurements. If you measure in metres, make sure all sides are in metres.

Parent and carer guide

Help your child understand perimeter by:
  • Looking at shapes around the house together
  • Measuring the edges of a table, book, or window
  • Using a ruler or tape measure to find the perimeter of objects
  • Playing the robot safe zone game together
  • Encouraging them to draw shapes and calculate the perimeter
You can also ask questions like:
  • How far would you walk if you went around the edge of your bedroom?
  • Can you find a shape in the garden and measure its perimeter?
  • What if we had a square room that was 5 metres on each side - how far would we walk?
Remember, the goal is not just to get the right answer but to understand what perimeter means. Let your child explore and make mistakes - that's how they learn best.

Practice questions

  1. What is the perimeter of a rectangle that is 8 metres long and 5 metres wide?
  2. Find the perimeter of a square with sides of 6 metres.
  3. A triangle has sides of 4, 5, and 7 metres. What is its perimeter?
  4. What is the perimeter of a rectangle that is 3 metres long and 2 metres wide?
  5. Calculate the perimeter of a square that is 10 metres on each side.
Answers:
  1. 8 + 8 + 5 + 5 = 26 metres
  2. 6 + 6 + 6 + 6 = 24 metres
  3. 4 + 5 + 7 = 16 metres
  4. 3 + 3 + 2 + 2 = 10 metres
  5. 10 + 10 + 10 + 10 = 40 metres

FAQ

What is perimeter?

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

How do you measure perimeter?

You measure perimeter by finding the length of each side of a shape and adding them all together. You can use a ruler or measuring tape to find the length of each side.

Can you find the perimeter of any shape?

Yes! You can find the perimeter of any shape as long as it has sides. Even shapes like triangles, squares, rectangles, pentagons, and hexagons all have perimeters.

What's the difference between area and perimeter?

Perimeter is the distance around the outside of a shape. Area is the space inside the shape. For example, a rectangle's perimeter is the total length of its edges, while its area is the space it covers inside.

Why do robots need to know perimeter?

Robots need to know perimeter to plan their paths, build safe zones, and understand how far they need to travel. It helps them navigate around obstacles and stay within safe boundaries.