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Maths Adventures

Time-travel maths quest: perimeter

A story-led junior maths adventure using clocks, calendars and ancient numbers 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 how far you'd walk around the outside of a garden or a fence.

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 clocks, calendars, and ancient numbers to help you measure distances in a time-travel adventure. Success signs:
  • You can find the perimeter of a rectangle by adding up all four sides
  • You can use a clock face to help you count around a shape
  • You can measure a safe zone around a castle wall using ancient number patterns
  • You can explain why perimeter matters in real life

Why this matters

Perimeter is like measuring how far you walk around a shape. It helps you plan things like building fences, designing playgrounds, or even exploring ancient castles. In a time-travel adventure, knowing the perimeter helps you find the safest path around a castle or measure how far you've walked through time. Think about when you walk around a football pitch or around your garden. That distance around the outside is the perimeter. In ancient times, people used to measure land by walking around it and counting their steps. Today, we use rulers, measuring tapes, and even clocks to help us find the perimeter.

How it works

To find the perimeter of a shape, you simply add up all the sides. Let's start with a simple square or rectangle:
  1. Look at each side of the shape
  2. Measure how long each side is
  3. Add all the measurements together
For example, if a rectangle has sides that are 5 cm, 3 cm, 5 cm, and 3 cm, the perimeter is: 5 + 3 + 5 + 3 = 16 cm You can also use a clock face to help you count around a shape:
  • Each number on a clock is 30 degrees apart
  • When you walk around a shape, you can count how many 30-degree jumps you make
  • This helps you measure angles and distances

Examples you can see

Let's imagine you're on a time-travel adventure. You're visiting an ancient Roman camp. The camp is shaped like a rectangle. Example 1: Roman Camp
  • The camp is 10 metres long and 6 metres wide
  • It has 4 sides: 2 long sides (10 m each) and 2 short sides (6 m each)
  • Perimeter = 10 + 6 + 10 + 6 = 22 metres
Example 2: Medieval Castle
  • The castle has a square courtyard
  • Each side of the courtyard is 8 metres
  • Perimeter = 8 + 8 + 8 + 8 = 32 metres
Example 3: Ancient Egyptian Pyramid
  • The base of the pyramid is a square
  • Each side is 20 metres
  • Perimeter = 20 + 20 + 20 + 20 = 80 metres

Try it as a mini adventure

Time-Travel Perimeter Quest You are a time-travelling explorer who has landed in ancient Egypt. Your mission is to measure the perimeter of the Great Pyramid of Giza to help archaeologists understand its construction. Step 1: You find a map showing the pyramid's base is a square.
  • Each side measures 200 metres
  • How far would you walk if you walked all the way around the base?
Step 2: You discover a Roman amphitheatre.
  • It is shaped like a rectangle
  • One side is 150 metres long, and the other side is 100 metres long
  • What is the perimeter of the amphitheatre?
Step 3: You find a medieval garden.
  • It is shaped like a hexagon (6 sides)
  • Each side is 5 metres long
  • What is the perimeter of the garden?
Step 4: You need to create a safe zone around the ancient building.
  • Each side of a square safe zone is 12 metres
  • How much rope do you need to mark the entire perimeter?

Common mistakes

  • Mistake: Forgetting to add all sides of a shape
    • Why it happens: Children may only add two sides instead of all four
    • Fix: Always count all sides and double-check with a friend or use a ruler to measure each one
  • Mistake: Confusing perimeter with area
    • Why it happens: Both involve shapes, so children mix them up
    • Fix: Remember: perimeter = distance around the outside, area = space inside the shape
  • Mistake: Not using the same units
    • Why it happens: Adding metres and centimetres without converting
    • Fix: Always convert all measurements to the same unit before adding
  • Mistake: Thinking perimeter only works for rectangles
    • Why it happens: Children only see rectangles in their examples
    • Fix: Any shape can have a perimeter, including triangles, pentagons, and hexagons

Parent and carer guide

Parents and carers can help children understand perimeter by:
  • Using everyday objects like books, boxes, or tables to measure perimeters
  • Walking around the house and measuring the perimeter of rooms or furniture
  • Using a clock face to count around shapes (like counting 12 jumps around a clock face to make 360 degrees)
  • Playing a game where you measure the perimeter of different shapes using rulers or measuring tapes
  • Encouraging children to draw shapes and write down the measurements of each side
What to say:
  • "Let's measure the perimeter of your bedroom"
  • "Can you find a shape in your room and add up all its sides?"
  • "How far would you walk if you went around the outside of this shape?"
What not to worry about:
  • Children may make mistakes – that's part of learning
  • They might mix up perimeter and area – that's normal and can be corrected with practice
  • They may not understand all the steps at first – that's okay, they'll get it with repetition

Practice questions

  1. What is the perimeter of a rectangle that is 7 cm long and 4 cm wide?
  2. A square garden has sides that are 9 metres long. What is its perimeter?
  3. A hexagon has sides that are all 6 cm long. What is its perimeter?
  4. What is the perimeter of a triangle with sides 5 cm, 7 cm, and 8 cm?
  5. A rectangular swimming pool is 12 m long and 8 m wide. What is its perimeter?
Answers:
  1. 7 + 4 + 7 + 4 = 22 cm
  2. 9 + 9 + 9 + 9 = 36 m
  3. 6 + 6 + 6 + 6 + 6 + 6 = 36 cm
  4. 5 + 7 + 8 = 20 cm
  5. 12 + 8 + 12 + 8 = 40 m

FAQ

What is perimeter?

Perimeter is the total distance around the edge of a shape. You can think of it as how far you'd walk if you went all the way around the outside of a shape.

How do I find the perimeter of a shape?

To find the perimeter, add up all the sides of the shape. For example, a rectangle with sides of 5 cm, 3 cm, 5 cm, and 3 cm has a perimeter of 5 + 3 + 5 + 3 = 16 cm.

Does every shape have a perimeter?

Yes! Every shape has a perimeter because you can always measure the distance around the outside of any shape, whether it's a triangle, square, circle, or more complex shape.

Why do we need to know about perimeter?

Knowing perimeter helps us in many real-life situations, like planning a fence around a garden, designing a playground, or even measuring how far you've walked around a track.

Can I use a clock to help measure perimeter?

Yes! You can use a clock face to help you count around a shape. For example, if you walk around a shape and count how many 30-degree jumps you make, you can use the clock to help you measure angles and distances.