Using formulae

We have already seen that and are examples of formulae. There are many others that we use regularly in other subjects. Sometimes we have to construct our own formula:

Example

A taxi firm charges per mile plus a fixed charge of . Write down a formula for the cost of hiring this taxi to travel miles.

Solution

• It costs to travel mile.
• It costs to travel miles.
• It costs to travel miles.

So traveling for miles will cost .

The formula is .

Note: .