Problem:
A driver travels for hours at miles per hour, during which her car gets miles per gallon of gasoline. She is paid per mile, and her only expense is gasoline at per gallon. What is her net rate of pay, in dollars per hour, after this expense?
Answer Choices:
A.
B.
C.
D.
E.
Solution:
Since the driver travels miles per hour and each hour she uses gallons of gasoline, she spends per hour on gas. If she gets per mile, then she gets per hour of driving. Subtracting the gas cost, her net rate of money earned per hour is .
The driver is driving for hours at miles per hour, she drives miles. Therefore, she uses
So, total she has
So, her rate is
The problems on this page are the property of the MAA's American Mathematics Competitions