Start from 110 feet away, a person on a bicycle rides towards a checkpoint and then passes it. The rider is travelling at a constant rate of 30 feet per second. The distance between the bicycle and the checkpoint is given by the equation d=|110-30t| at what times is the bike 40 feet away from the checkpoint?

a. 2.3 sec and 5 sec
b. 1.6 sec and 5 sec
c. 2.3 sec and 4.6 sec
d. 1.6 sec and 4.6 sec

6 answers

I choose c

|110-30t| = 40
so, either

110-30t = 40
30t = 70
t = 7/3 = 2.3

or

-(110-30t) = 40
-110+30t = 40
30t = 150
t = 5

So, (A) is correct

Thank you so much!

Steve definitely got it right!

Just did the test still correct in 2020!!!

Thanks Steve!