The imperial system of units was defined in the British Weights and Measures Act and came into official use across the British Empire.
Although all nations of the former British Empire have officially adopted the International System of Units as their main system of measurement, some countries such as Canada still unofficially use the Imperial System (in some instances).
Length is commonly expressed using the following units from the Imperial System of Units.
Some other less common units of length in the Imperial System are the furlong, league, cable, link, pole and chain.
In mathematics we will concentrate only on the inch, foot, yard and the mile.
In the Imperial System of Units, area is usually expressed using the units perch, rood (or rod) and acre.
Rather than use the basic units listed above, most mathematicians use the compound units of the square inch (in2 or sq in), square foot (ft2 or sq ft), square yard (yd2 or sq yd) and the square mile (mi2 or sq mi) as units of area.
In the Imperial System of Units, volume is usually expressed using the units fluid ounce, pint, quart and gallon.
Rather than use the basic units listed above, most mathematicians use the compound units of the cubic inch (in3 or cu in), cubic foot (ft3 or cu ft), cubic yard (yd3 or cu yd) and the cubic mile (mi3 or cu mi) as units of volume.
Other measures such as mass (and weight), temperature, quantity of matter, electric current, luminous intensity, density etc. have unique units different from those in the International System of Units.
At this level, we will concern ourselves only with Imperial units for measures of length, area and volume, as outlined above.
We will also be concerned with compound addition and subtraction of Imperial units as well as converting between measures in the International System of Units and the Imperial System of Units.