Average speed of a vehicle

Question

The average speed of a vehicle on a stretch of Route 134 between 6 A.M. and 10 A.M. on a typical weekday is approximated by the function

f(t) = 30t − 60 t + 70

(0 ≤ t ≤ 4)

where f (t) is measured in miles per hour, and t is measured in hours, with t = 0 corresponding to 6 A.M.

At what time of the morning commute is the traffic moving at the slowest rate?

 

What is the average speed of a vehicle at that time?

 

Answer 1