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Mathematics>Standard Multiple Choice

Read the following SAT test question and then click on a button to select your answer.

A rental car company charges $45 per day for the rental of a midsize car. Additionally, there is a tax of 8% on all car rentals. Which of the following functions c best represents the total charge, including tax, in dollars, to rent the midsize car for d days?

A.c(d)=45.08d
B.c(d)=45d+1.08
C.c(d)=45*0.08d
D.c(d)=45*1.08d

答案和解析

答案：D

解析：

Since the daily charge for the car is $45, the tax rate is 8%, and the rental is for d days, the total rental charges can be represented by the expression 45*1.08*d.

Note that adding an 8% tax to the original amount is the same as using 108% of the original amount, which is achieved by multiplying by 1.08.

Since c(d) represents the total rental charges, including tax, over d days, the function that best models this is: c(d)=45*1.08d.