Bunuel
When Mark fills his car with regular gasoline, he gets 20 miles/gallon. When he fills his car with premium gasoline, he gets 25 miles/gallon. If the price of regular gasoline is $4.00 per gallon and the price of premium gas is $6.25 per gallon, then the cost efficiency of regular gasoline, in miles/dollar, is what percent greater than the cost efficiency of premium gasoline?
(A) 4%
(B) 10%
(C) 20%
(D) 25%
(E) 50%
We can create the equation:
(20/4 - 25/6.25)/(25/6.25) x 100
(5 - 4)/4 x 100
1/4 x 100 = 25
Alternate Solution:
Let’s calculate the cost of driving 100 miles using each type of gasoline.
Using regular gasoline, he would need 100/20 = 5 gallons, and this would cost him 5 * 4 = 20 dollars. Thus, the cost efficiency of regular gasoline is 100/20 = 5 miles/dollar.
Using premium gasoline, he would need 100/25 = 4 gallons, and this would cost him 4 * 6.25 = 25 dollars. Thus, the cost efficiency of premium gasoline is 100/25 = 4 miles/dollar.
We see that regular gasoline is (5 - 4)/4 x 100 = 25% more cost efficient than premium gasoline.
Answer: D