Interpreting formulae
A An equation that is written for a purpose, such as converting Fahrenheit to Celsius. A formula is always true regardless of the values used. is an equation that shows the relationship between A quantity that can change or that may take on different values. Variable also refers to a letter or symbol representing such a quantity.. These variables could be:
- the cost of hiring a worker based on the number of hours worked
- the cost of hiring a van based on the number of days it is needed for
A formula can be expressed as a worded problem or as an An equation contains an equals sign. Equations are only true for certain values. using words or letters.
Example 1
Cost of hiring a van = number of days × £40 + £100
This formula allows you to calculate the cost of hiring a van based on the number of days it is needed for.
As you can see, there is a flat charge of £100 no matter how many days it is needed for.
For each day it is needed £40 is added to this cost.
Example 2
Gareth is a electrician. He charges a call-out fee of £45 in addition to £15 for every hour on the job.
This can be re-written as an equation:
Wages = number of hours × £15 + £45.
