Question

Your friend has $90 when he goes to the fair. He spends $5 to enter the fair and $15 on food. Rides at the fair cost $1.50 per ride. Which function can be used to determine how much money he has left over after x rides?

Answer 1

Easy, if he has $90 in ALL

and he spends $5 and $15

$20 in total

take, 90-20=70

So now he only has $70 left.

If each ride costs $1.50, then he's losing money.

So, y=-1.50x+70

So around the 47th ride he will have no more money.

Answer 2

`f(x)=70-1.5x` or
`f(x)=-1.5x+70`

Explanation:

Money taken to the fair = $90

Money spent to enter the fair = $5

Money spent on food =$15

Total he spent now is given by :
`5+15=20` dollars

Let the number of rides be = x

And he spends $1.50 on each ride, so total money spent on rides =
`1.50x`

Total money including rides can be shown as:

`20+1.50x`

Now money left after this will be
`90-(20+1.50x)`

=
`70-1.50x`

Let f(x) denotes the function used to determine the money left after rides,

`f(x)=70-1.5x` or
`f(x)=-1.5x+70`