Four gallons of gasoline for 16.80 . What is the price of gasoline in terms of gasoline per dollor

Question

 It is hard

Answer 1

 

One way to make this easier is to write the units.

 

You have $16.80 / 4 gallons.   That's  $4.20 per gallon, or we can write  4.20 dollars/gallon.

 

Since you want gallons per dollar, just invert the 4.20:

 

    N gallons / dollar = (1/N) dollars / gallon:  

 

    1/ (4.20 dollars/gallon) = 0.2381 gallons / dollar.

 

I hope this makes sense. 

 

(Sanity) Check:  0.2381 gallons for $1   … That's a little less than one quarter gallon for $1, so if I wanted an entire gallon it would be a little over $4.  Looks reasonable.   

 

 

Answer 2

First, lets calculate how much a gallon of gasoline cost.

 

Since 4 gallons cost $16.80,

           1 gallon cost   $16.80 / 4 = $4.20

 

The question is asking gasoline PER dollar, but what you have is dollars per gallon. We need to rewrite the answer in terms of a dollar.

 

Since $4.20 buys a gallon of gasoline,

           $1 buys 1 gallon / 4.20

            =  0.238 gallons/dollar