Q:

Starting from 300 feet away, a car drives toward you. It then passes by you at a speed of 48 feet per second. The distance dd (in feet) of the car from you after tt seconds is given by the equation ​d=|300−48t|​d=|300−48t|. At what times is the car 60 feet from you?​

Accepted Solution

A:
Givend = |300 -48t|Findt when d=60SolutionPut in the value for d and solve.60 = |300 -48t|This resolves to two equations:First-60 = 300 -48t . . . . the absolute value changes the sign of its content0 = 360 -48t . . . . . add 600 = 7.5 -t . . . . . . . . divide by 48t = 7.5Second60 = 300 -48t . . . . . the absolute value leaves the sign of its content unchanged0 = 240 - 48t . . . . . . subtract 600 = 5 - t . . . . . . . . . . divide by 48t = 5SummaryThe car is 60 feet from you at times t=5 seconds and t=7.5 seconds.