Pirate 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 and calculate the perimeter of different shapes using addition.

• You can identify the sides of a shape
• You can add up all the sides to find the perimeter
• You can use a ruler or measuring tape to measure shapes
• You can solve real-life problems using perimeter

Why this matters

Perimeter is like a treasure map's boundary line. When you're a pirate, you need to know how far your safe zone is from the edge of your island. In real life, you use perimeter when you want to put a fence around your garden, or when you're planning how much ribbon you need to go around a gift box. It helps you understand how much space something takes up around its edge.

How it works

Perimeter means the total distance around a shape. To find it:

1. Look at all the sides of the shape
2. Measure each side
3. Add all the measurements together
4. Write your answer with the correct unit (like metres or centimetres)

For example, if a shape has sides that are 3cm, 4cm, 3cm, and 4cm, you add them up: 3 + 4 + 3 + 4 = 14cm.

Examples you can see

Let's imagine you're on a pirate adventure! You need to find the perimeter of your treasure island.

Example 1: Square island

Your island is a square with each side measuring 5 metres. To find the perimeter:

• Side 1: 5m
• Side 2: 5m
• Side 3: 5m
• Side 4: 5m
• Total: 5 + 5 + 5 + 5 = 20m

Example 2: Rectangular island

Your island is rectangular, 6 metres long and 4 metres wide. To find the perimeter:

• Long side: 6m
• Short side: 4m
• Long side: 6m
• Short side: 4m
• Total: 6 + 4 + 6 + 4 = 20m

Example 3: Triangle island

Your island is triangular with sides of 3m, 4m, and 5m:

• Side 1: 3m
• Side 2: 4m
• Side 3: 5m
• Total: 3 + 4 + 5 = 12m

Try it as a mini adventure

Pirate Treasure Island Quest

You are Captain Maths, and you've found a treasure map! To find the treasure, you must measure the perimeter of different safe zones on the island.

Step 1: You see a rectangular safe zone that is 8m long and 5m wide.

Step 2: You must find the perimeter to know how much rope you need to make a fence.

Step 3: Draw a rectangle that is 8m by 5m and add up all the sides.

Step 4: You see a square safe zone that is 6m on each side.

Step 5: Calculate the perimeter of the square.

Step 6: You find a triangular safe zone with sides of 4m, 5m, and 6m.

Step 7: Add up the sides to find the perimeter.

Step 8: The treasure is hidden where the total perimeter of all three zones equals 30m.

Common mistakes

• Mistake: Forgetting to measure all sides

  Why it happens: When measuring, children might only measure some sides and forget to include all of them.

  Fix: Count the sides of the shape and make sure you measure each one. Use your finger to trace around the shape to help you remember which sides to measure.

• Mistake: Adding the wrong measurements

  Why it happens: Children may add numbers that don't match the sides they measured.

  Fix: Write down each measurement clearly before adding them. Use a ruler to double-check your measurements.

• Mistake: Not using the right unit

  Why it happens: Children may forget to include units like metres or centimetres in their answer.

  Fix: Always remember to add the correct unit after your final answer. If you're measuring a small shape, use centimetres. For bigger shapes, use metres.

Parent and carer guide

Helping your child with perimeter is easy and fun! Here are 5-10 minutes of practical support:

• Find shapes around your home like a book, a table, or a window
• Ask your child to measure the sides and add them up
• Use a ruler or measuring tape to help them measure accurately
• Draw the shape together and label each side
• Encourage them to explain how they found the perimeter
• Play a game where you measure different objects and compare their perimeters
• Use real-life examples like measuring the edge of a garden or a swimming pool
• Don't worry if they make mistakes – it's part of learning!
• Ask questions like "How many sides did you measure?" or "What unit did you use?"
• Make it fun by pretending you're explorers or pirates measuring treasure islands!

Practice questions

1. What is the perimeter of a square with sides of 7m?
2. What is the perimeter of a rectangle that is 10m long and 4m wide?
3. What is the perimeter of a triangle with sides of 5m, 6m, and 7m?
4. What is the perimeter of a rectangle that is 3m long and 2m wide?
5. What is the perimeter of a square with sides of 9m?
6. What is the perimeter of a triangle with sides of 4m, 4m, and 4m?
7. What is the perimeter of a rectangle that is 8m long and 3m wide?
8. What is the perimeter of a square with sides of 5m?
9. What is the perimeter of a triangle with sides of 3m, 5m, and 7m?
10. What is the perimeter of a rectangle that is 6m long and 2m wide?

Answers:

1. 28m
2. 28m
3. 18m
4. 10m
5. 36m
6. 12m
7. 22m
8. 20m
9. 15m
10. 16m

FAQ

What is perimeter?

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

How do I measure perimeter?

Measure each side of the shape, then add all the measurements together. Don't forget to include the correct unit (like metres or centimetres).

Can I find the perimeter of any shape?

Yes! You can find the perimeter of any shape that has sides, like squares, rectangles, triangles, and even irregular shapes.

Why do I need to know perimeter?

Perimeter helps you solve real-life problems like knowing how much fencing you need for a garden, or how far you need to walk around a park.

How is perimeter different from area?

Perimeter is the distance around the edge of a shape, while area is the space inside the shape. Perimeter is measured in units like metres, and area is measured in square units like square metres.