Area, Perimeter and Volume
How much paint, how many floor tiles, how much soil for the planter? These three ideas answer all of them.
~10 min3 lessonsProject calculator5-question quiz
01
Perimeter: the distance around
Perimeter is the total length of the edges, like the fence around a garden. Just add up the sides.
Example · a 5 m × 3 m garden
- 5 + 3 + 5 + 3
- 16 m of fencing
For a circle, the distance around is the circumference: π × diameter, about 3.14 × the distance across.
02
Area: the space inside
Area is measured in square units (m², ft²): how many 1 × 1 squares would cover the shape.
| Shape | Area |
|---|---|
| Rectangle | length × width |
| Triangle | ½ × base × height |
| Circle | π × radius² (radius = half the width) |
Example · paint for a 4 m × 2.5 m wall, one door
- Wall: 4 × 2.5 = 10 m²
- Door (about 2 m × 0.8 m): 1.6 m²
- Paint: 10 − 1.6 = 8.4 m², × 2 coats = 16.8 m²
- Check the tin: if 1 litre covers 12 m², you need about 1.4 litres
Units trap: 1 m² is not 100 cm². It's 100 cm × 100 cm = 10,000 cm².
03
Volume: how much fits inside
Volume is measured in cubic units (m³, cm³) or litres. 1 litre = 1,000 cm³, and 1 m³ = 1,000 litres.
| Shape | Volume |
|---|---|
| Box (cuboid) | length × width × height |
| Cylinder | π × radius² × height |
Example · soil for a 1.2 m × 0.4 m planter, 0.3 m deep
- 1.2 × 0.4 × 0.3 = 0.144 m³
- × 1,000
- 144 litres of soil
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