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:
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:
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.
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.
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 travelling for miles will cost 
.
The formula is 
.
Note: 
.
- QQuestion
-
A rectangle has a width of
and a length of 
.
Write down a formula for the perimeter 
in terms of .
-
-
Did you remember to include all
sides?
So 
- It costs
- It costs
- It costs
So travelling for miles will cost .
miles will cost .
The formula is .
.
Note: .
.- QQuestion
- A rectangle has a width ofWrite down a formula for the perimeter
- Did you remember to include allSo
