Measure around shapes and count the space inside!
Perimeter is the total distance around the outside of a shape. Add up all the side lengths.
For a rectangle with length l and width w:
Example: l = 8 cm, w = 3 cm → P = 2 × (8 + 3) = 2 × 11 = 22 cm
Area is the amount of space inside a shape. We measure area in square units (cm², m²).
Example: l = 6 cm, w = 4 cm → A = 6 × 4 = 24 cm²
You can find area by counting how many unit squares fit inside the shape.
Each small square on a grid = 1 cm². Count all the full squares to find the area.
A shape 5 squares wide and 3 squares tall has area = 5 × 3 = 15 cm²
If you know the perimeter and one side, find the other side:
If you know the area and one side:
Example: A = 35 cm², l = 7 cm → w = 35 ÷ 7 = 5 cm
Read carefully — are you asked for perimeter (distance around) or area (space inside)?
| Clue words | You need |
|---|---|
| fence, border, frame, edge | Perimeter |
| tiles, carpet, lawn, floor, surface | Area |
A rectangle has length 9 cm and width 4 cm. Find the perimeter.
A rectangle has length 7 cm and width 5 cm. Find the area.
A rectangle has perimeter 28 cm and length 9 cm. Find the width.
A rectangle has area 48 cm² and length 8 cm. Find the width.
Use P = 2(l + w) to find the perimeter of each rectangle.
Use A = l × w to find the area of each rectangle.
Find the missing width given the perimeter and length.
Find the missing width given the area and length.
Solve each problem. Decide if you need perimeter or area.