Question

Darnell's car used 8 gallons of gasoline to travel 340 miles. after a mechanic worked on the car, it used 7 gallons of gasoline to travel 350 miles. If the price of the gasoline was approximately $4.00 per gallon, how much lest to the nearst cent per mile, did it cost to run the car after the mechanic worked on it?

Answer 1

So, after the mechanic worked on it, it only does 7 gallons for 350miles, how many gallons will it be at that rate, for 340 miles then?

$\bf \begin{array}{ccll} gallons&miles\\ \text{\textemdash\textemdash\textemdash}&\text{\textemdash\textemdash\textemdash}\\ 7&350\\ x&340 \end{array}\implies \cfrac{7}{x}=\cfrac{350}{340}\implies \cfrac{7\cdot 340}{350}=x\implies 6.8=x$

well, each gallon is 4 bucks, for 6.8 gallons that'd be 6.8*4.

we already know that before the mechanic worked on it, it was doing 8gallons for the same 340 miles, and at 4 bucks a gallon that'd be 8*4.

how much is her savings?

$\bf \stackrel{\stackrel{\textit{gallons cost}}{\textit{before being fixed}}}{(8\cdot 4)}\qquad -\qquad \stackrel{\stackrel{\textit{gallons cost}}{\textit{after it was fixed}}}{(6.8\cdot 4)}$