1 Using units of measurement

Everyday problems where you want to determine how much there is of a quantity involve measurement. Things are measured for a variety of different reasons, but in everyday life this is usually to find out how big, how long or how heavy something is, or its volume, length or mass.

For these numbers to have any meaning, you need to specify what units the measurement is in. If you were told that it was ‘three’ to the nearest hospital that wouldn’t be much good unless you knew the units as well. Is that three feet, three metres, three miles or three kilometres? Each is a very different distance from you. So, it is very important when dealing with measurements to always state the units being used.

The units will also tell you what system of measurement has been used. Most of the scientific world has adopted an internationally agreed system of measurement, using metric units such as metres and litres. The rules for their use form the Système Internationale (International System), simply known as the SI, whereas in everyday life you may still be using some imperial units, such miles and pints. The system you prefer will depend on what you are most comfortable with. This course looks at both systems of measurement because you probably encounter both in your daily life. This may well also be the case in any university level study. Although, most work will be carried out using the SI, it may be that work from other countries, such as the USA, and historical studies will employ imperial measures.

The next section starts with a look at how the SI is put together generally and then moves onto the SI and imperial units when working with length.