The ‘moving walkway’ is a 300-foot long conveyor belt that moves continuously at 3 feet per second. When Bill steps on the walkway, a group of people that are also on the walkway stands 120 feet in front of him. He walks toward the group at a combined rate (including both walkway and foot speed) of 6 feet per second, reaches the group of people, and then remains stationary until the walkway ends. What is Bill’s average rate of movement for his trip along the moving walkway?
2 feet per second
2.5 feet per second
3 feet per second
4 feet per second
5 feet per second
Ive seen this somewhere. Anyway forget the conveyor belt speed for now.
Bills speed is 3ft per sec. so T=D/R T=120/3 ---> T1=40sec.
However, note that in this 40 sec bill didn't just travel 120 feet. He actually traveled 240feet. You have to count the 3ft per sec of the conveyor belt now. I just ignored that speed to make things easier to calculate.
So he has 60feet left @3ft per sec. T2=60/3 = 20 sec.
Now average Rate = Total D/ Total Time
300ft/(40+20)sec ---> 300/60 = 5ft per/sec.