Table of Contents

🔍 Detailed Explanation of the Topic: Perimeter

Perimeter is all about finding the distance all around the edge of a shape. Imagine you want to walk all the way around a playground. The total distance you walk is like the perimeter of the playground.

❓ What is Perimeter?

Perimeter means the length around a shape. You add up the length of all the sides to find the perimeter. It tells you how far it is to go all the way around.

📐 Examples of Perimeter with Common Shapes

  1. Square
    A square has 4 sides that are all the same length.
    If one side of the square is 3 centimetres, the perimeter is:
    3 + 3 + 3 + 3 = 12 centimetres
    Or you can multiply: 4 × 3 = 12 centimetres
  2. Rectangle
    A rectangle has 4 sides. The opposite sides are the same length.
    If one long side is 5 centimetres and one short side is 2 centimetres, the perimeter is:
    5 + 2 + 5 + 2 = 14 centimetres
    Or you can add the lengths of two different sides and multiply by 2:
    (5 + 2) × 2 = 14 centimetres
  3. Triangle
    A triangle has 3 sides. You add all the sides together to find the perimeter.
    If the three sides are 3 centimetres, 4 centimetres, and 5 centimetres:
    3 + 4 + 5 = 12 centimetres

🧮 How to Calculate Perimeter Step by Step

  1. Look at the shape and find the length of each side.
  2. Add all the side lengths together.
  3. The answer you get is the perimeter.

💡 Tips for Measuring and Calculating Perimeter

  • Make sure to measure all sides carefully.
  • Remember to use the same units, like centimetres or metres.
  • Add or multiply the numbers clearly to avoid mistakes.

Perimeter helps us know the length all around a shape, which is useful for things like fencing a garden or framing a picture. Keep practising by measuring different shapes around you!

📝 20 Examination-Style Questions on Perimeter for Year 3 Maths

These 20 perimeter questions are made especially for Year 3 students learning maths under the UK National Curriculum. They include calculating the perimeter of different shapes, word problems, and real-life application questions.

📏 Calculating Perimeter of Shapes

  1. What is the perimeter of a rectangle with lengths 7 cm and widths 3 cm?
  2. Find the perimeter of a square with sides of 5 cm.
  3. A triangle has sides of 6 cm, 4 cm, and 5 cm. What is its perimeter?
  4. Calculate the perimeter of a rectangle that has a length of 9 cm and a width of 2 cm.
  5. The sides of a square are 8 cm long. What is its perimeter?
  6. A pentagon has five sides each 3 cm long. What is the perimeter?
  7. Find the perimeter of a triangle with sides 5 cm, 5 cm, and 8 cm.
  8. A rectangle has a perimeter of 24 cm. If its length is 7 cm, what is the width?

📝 Word Problems on Perimeter

  1. Sarah has a garden shaped like a rectangle. It is 10 m long and 6 m wide. How much fencing does she need to go all around her garden?
  2. A frame is shaped like a square and the perimeter is 20 cm. How long is each side?
  3. Tom walks around a rectangular park. The park is 15 m long and 8 m wide. How far does Tom walk around the park?
  4. A triangular playground has sides of 12 m, 8 m, and 10 m. What is the total length of the fence needed to go all around it?
  5. A square window has a perimeter of 16 m. Find the length of one side of the window.
  6. Lucy bought a ribbon that is 30 cm long to put around a rectangular box. The box is 8 cm long and 7 cm wide. Will she have enough ribbon?

🔧 Application-Based Questions

  1. A rectangular swimming pool is 20 m long and 10 m wide. Calculate the perimeter of the pool.
  2. A football field is 100 m long and 60 m wide. What is the perimeter of the football field?
  3. A rectangular table is 4 m long and 2 m wide. What is the total length around the table if you put a tablecloth around it?
  4. A square picture frame has sides of 30 cm. Find the perimeter of the frame.
  5. The perimeter of a rectangular room is 28 m. If the width is 6 m, what is the length of the room?
  6. A rectangular garden has a length that is double its width. If the width is 4 m, what is the perimeter of the garden?

These perimeter questions help practice calculating distances around various shapes and solving problems like those in real-life situations. Remember, perimeter means adding all the sides to find the total length around the shape!

✅ Answers of the Examination-Style Questions on Perimeter for Year 3

Below are clear, step-by-step answers to 20 examination-style questions about perimeter, designed for Year 3 students in Key Stage 2. These explanations will help you understand how to find the perimeter of different shapes easily.

❓ What is Perimeter?

Perimeter is the total distance all around the outside of a shape. To find the perimeter, you add up the lengths of all the sides.

Question 1: Find the perimeter of a rectangle with sides 5 cm and 3 cm.

Answer:
Add up all sides: 5 + 3 + 5 + 3 = 16 cm
So, the perimeter is 16 cm.

Question 2: A square has sides of 4 cm. What is its perimeter?

Answer:
All sides are equal, so add 4 + 4 + 4 + 4 = 16 cm
Perimeter = 16 cm.

Question 3: A triangle has sides: 3 cm, 4 cm and 5 cm. Find the perimeter.

Answer:
Add all the sides: 3 + 4 + 5 = 12 cm
The perimeter is 12 cm.

Question 4: A rectangle has a length of 7 cm and a width of 2 cm. What is the perimeter?

Answer:
Perimeter = 7 + 2 + 7 + 2 = 18 cm.
Answer: 18 cm.

Question 5: If each side of a square is 6 cm, find the perimeter.

Answer:
4 sides × 6 cm = 24 cm.
Perimeter = 24 cm.

Question 6: A shape has 3 sides of 5 cm, 7 cm and 5 cm. What is the perimeter?

Answer:
Add the sides: 5 + 7 + 5 = 17 cm.
Perimeter = 17 cm.

Question 7: Find the perimeter of a rectangle with sides 9 cm and 4 cm.

Answer:
9 + 4 + 9 + 4 = 26 cm.
Perimeter = 26 cm.

Question 8: A square has a perimeter of 20 cm. What is the length of one side?

Answer:
Perimeter ÷ 4 = side
20 ÷ 4 = 5 cm
Length of one side is 5 cm.

Question 9: A triangle has sides 8 cm, 6 cm and 7 cm. Find its perimeter.

Answer:
8 + 6 + 7 = 21 cm
Perimeter = 21 cm.

Question 10: Find the perimeter when one side is 10 cm and all sides are equal (square).

Answer:
4 × 10 = 40 cm
Perimeter = 40 cm.

Question 11: A rectangle has a length of 12 cm and width of 3 cm. What is the perimeter?

Answer:
12 + 3 + 12 + 3 = 30 cm
Perimeter = 30 cm.

Question 12: Find the perimeter of a triangle with sides 5 cm, 5 cm and 8 cm.

Answer:
5 + 5 + 8 = 18 cm
Perimeter = 18 cm.

Question 13: A square has sides of 7 cm. Find its perimeter.

Answer:
4 × 7 = 28 cm
Perimeter = 28 cm.

Question 14: The sides of a rectangle are 15 cm and 4 cm. Find the perimeter.

Answer:
15 + 4 + 15 + 4 = 38 cm
Perimeter = 38 cm.

Question 15: Find the perimeter of a triangle with sides 9 cm, 7 cm and 6 cm.

Answer:
9 + 7 + 6 = 22 cm
Perimeter = 22 cm.

Question 16: A square has a perimeter of 32 cm. What is one side length?

Answer:
32 ÷ 4 = 8 cm
One side is 8 cm.

Question 17: The sides of a rectangle are 18 cm and 2 cm. Find the perimeter.

Answer:
18 + 2 + 18 + 2 = 40 cm
Perimeter = 40 cm.

Question 18: A triangle’s sides are 10 cm, 10 cm and 10 cm. What is the perimeter?

Answer:
10 + 10 + 10 = 30 cm
Perimeter = 30 cm.

Question 19: Find the perimeter of a square with side 9 cm.

Answer:
4 × 9 = 36 cm
Perimeter = 36 cm.

Question 20: Find the perimeter of a rectangle with sides 11 cm and 5 cm.

Answer:
11 + 5 + 11 + 5 = 32 cm
Perimeter = 32 cm.

Remember: To find the perimeter, always add all the sides together. For rectangles and squares, you can use multiplication because some sides are equal. Practice these steps, and you will find perimeters quickly and accurately!