Question

Starting from 1.6 miles away, a car drives toward a speed checkpoint and then passes it. The car travels at a constant rate of 53 miles per hour. The distance of the car from the checkpoint is given by d = |1.6 – 53t|. At what times is the car 0.5 miles from the checkpoint? Calculate your answer in seconds.

Answer 1

0.5 = |1.6-53t|
so 1.6-53t could be 0.5 or -0.5
Case 1: 0.5 = 1.6-53t
0 = 1.1-53t
53t=1.1
t=0.02075 hours * 3600 seconds per hour = 74.717 seconds
Case 2: -0.5 = 1.6-53t
0 = 2.1-53t
53t=2.1
t=0.03962 hours * 3600 seconds per hour = 142.642 seconds