Changing between units of measurement
There are two systems used for measuring quantities - metric and imperial.
The metric system uses three main units for measuring:
- length in metres (m)
- mass in kilograms (kg)
- volume in cubic metres (m3)
The imperial system uses the following units:
- length in inches, feet and yards
- mass in pounds (lb), ounces (oz) and stones
- volume in gallons
Converting metric units of length
The most common metric unit conversions for length are:
- 1 km = 1,000 m
- 1 m = 100 cm
- 1 cm = 10 mm
- 1 m = 1,000 mm
These can be used to convert the units used to measure length.
Example
The sunflower is 214 cm tall. Calculate the height of the sunflower in metres and millimetres.
There are 100 centimetres in a metre.
\(214 \div 100 = 2.14~\text{m}\)
There are 10 millimetres in a centimetre.
\(214 \times 10 = 2140~\text{mm}\)
It is not always easy to decide whether to divide or multiply by the A number that translates one particular unit or value into another..
Metres are larger than centimetres so the number of centimetres will be larger than the number of metres. Divide the number of centimetres by the conversion factor.
Millimetres are smaller than centimetres so the number of millimetres will be larger than the number of centimetres. Multiply the number of centimetres by the conversion factor.
Check the answer - should it be smaller or larger than the original number?