Example 1
Change 3 m into centimetres.
- There are 100 cm in 1 m.
- Centimetres are smaller than metres, so multiply by 100.
- 3 × 100 = 300
So: 3 m = 300 cm
Back to National 3
Topic
Measurement
Measurement questions use units, simple conversions, scale drawings, perimeter, and sensible choices in practical situations.
Topic explanation
Always check the unit before calculating. A correct number with the wrong unit can still be wrong.
For common conversions, use the fact you know: 100 cm = 1 m, 1000 g = 1 kg, and 1000 ml = 1 litre.
Scale drawings use a fixed relationship. If 1 cm stands for 4 m, then 2 cm stands for 8 m.
Quick methods
- Length
- 100 cm = 1 m and 1000 m = 1 km
- Mass
- 1000 g = 1 kg
- Capacity
- 1000 ml = 1 litre
- Perimeter
- Add all outside lengths.
Worked examples
Example 2
A rectangle is 8 cm long and 5 cm wide. What is its perimeter?
- Perimeter means the distance around the outside.
- Add all four sides: 8 + 5 + 8 + 5.
- 8 + 5 + 8 + 5 = 26
So: The perimeter is 26 cm.
Example 3
On a scale drawing, 1 cm represents 4 m. A path is 3 cm on the drawing. What is the real length?
- Each 1 cm on the drawing stands for 4 m in real life.
- Multiply the drawing length by 4.
- 3 × 4 = 12
So: The real path length is 12 m.