SAT Math Multiple Choice Practice Question 77: Answer and Explanation
11. Owen needs to travel 400 miles in 8 hours. If he averages m miles per hour for the first three hours, what does his average speed need to be for the remaining 5 hours?
D. 50 - m/3
E. 80 - 3m
Correct Answer: A
A. You know that distance = speed × time, so Owen has traveled 3m miles so far. That journey leaves him with 400 - 3m miles still to go in 5 hours. Because distance = speed × time, speed = distance/time, and Choice (A) is your answer.