Over a specified distance, speed varies inversely with time. If Joe can drive from his house to his office in 40 minutes at an average speed of 40 miles per hour, what average speed is needed to
Drive the same distance in half an hour? If necessary, round your answer to the nearest tenth.
A)50 miles per hour
B)60 miles per hour
C)30 miles per hour
D)53.3 miles per hour

Question

Quizplus · Accepted Answer

Speed varies inversely with time, so speed = k/time. If Joe can drive from his house to his office in 40 minutes at an average speed of 40 miles per hour, then 40 = k/40, so k = 1600. To drive the same distance in half an hour, the average speed needed is 1600/30 = 53.3 miles per hour.

Over a Specified Distance, Speed Varies Inversely with Time