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

Question

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

perl · Answer

solve   40 = 110 - 30*t   
and     -40 = 110 - 30*t

perl · Answer

so i get t = 5 , 2.3

perl · Answer

you can be 40 feet to the right or left of the origin. thats why you have two equations

anonymous · Answer

ok got it, so A?