Mathematics > Standard Multiple Choice
Read the following SAT test question and then click on a button to select your answer.
A mechanic can install carburetors in 3 cars every 4 hours. At that rate, how long will it take the mechanic to install carburetors in 5 cars?
(A) 6 hr 20 min
(B) 6 hr 40 min
(C) 7 hr 15 min
(D) 7 hr 30 min
(E) 7 hr 45 min
The correct answer is B
Explanation
From the information given, you can write the proportion 3 cars is to 4 hours as 5 cars is to x hours, where x represents the number of hours the mechanic will take to install carburetors in 5 cars. This gives 3 cars / 4 hours = 5 cars / x hours, which simplifies to 3 x = 4 *5 = 20. Therefore, x = 20 over 3 = 6 and (2 over 3) hours. Since 2 over 3 hour is 40 minutes, x is 6 hours 40 minutes.
