Perimeter — Grade 2 Mathematics

The perimeter of a shape is the total distance around its outside edge. Imagine an ant walking all the way around the boundary — the distance it travels is the perimeter!

What is Perimeter?

Perimeter = the sum of all sides of a shape.

For any polygon: P = side₁ + side₂ + side₃ + …

For a rectangle (length l, width w):
P = 2 × l + 2 × w = 2(l + w)

For a square (side s): P = 4 × s

Visualising a Rectangle's Perimeter

8 cm 8 cm 4 cm 4 cm

P = 8 + 4 + 8 + 4 = 24 cm or 2(8 + 4) = 2 × 12 = 24 cm

Worked Examples

Example 1 — Perimeter of a Rectangle

A rectangle is 9 cm long and 5 cm wide. Find its perimeter.

Use the formula: P = 2(l + w)
P = 2(9 + 5) = 2 × 14 = 28 cm

Example 2 — Perimeter of a Triangle

A triangle has sides 6 cm, 8 cm, and 10 cm. Find the perimeter.

P = 6 + 8 + 10
P = 24 cm

Example 3 — Real World: Fencing a Garden 🌿

Mrs. Ali wants to put a fence around her rectangular garden which is 12 m long and 7 m wide. How much fencing does she need?

Perimeter = 2(l + w)
= 2(12 + 7) = 2 × 19 = 38 m

She needs 38 metres of fencing.

Practice Questions

Work out the perimeter for each shape.

1. A rectangle is 10 cm long and 3 cm wide. What is its perimeter?

✅ P = 2(10 + 3) = 2 × 13 = 26 cm

2. A square has sides of 7 cm. What is its perimeter?

✅ P = 4 × 7 = 28 cm

3. A triangle has sides of 5 cm, 9 cm, and 6 cm. What is its perimeter?

✅ P = 5 + 9 + 6 = 20 cm

4. A rectangle has a perimeter of 30 cm and a length of 10 cm. What is the width?

✅ 2(10 + w) = 30 → 10 + w = 15 → w = 5 cm

5. A square has a perimeter of 36 cm. How long is each side?

✅ 36 ÷ 4 = 9 cm

Key Points to Remember

Perimeter = sum of all sides (add them all up).
Rectangle: P = 2(l + w).
Square: P = 4s.
Perimeter is measured in units of length (cm, m, etc.).
To find a missing side: subtract the known sides from the total perimeter.

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