VeritasPrepKarishma wrote:

Gmatter111 wrote:

The ‘moving walkway’ is a 300-foot long walkway consisting of a 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 rate of 3 feet per second. Once Bill reaches the group of people, he stops walking and stands with them until the walkway ends. What is Bill’s average rate of movement for his trip along the moving walkway?

A. 2 feet per second

B. 2.5 feet per second

C. 3 feet per second

D. 4 feet per second

E. 5 feet per second

Using relative speed concepts:

Bill covers 120 feet at a relative speed of 6 - 3 = 3 feet/sec. Time taken to cover 120 feet = 120/3 = 40 sec

Distance covered in 40 secs = 6*40 = 240 feet

So now he just has 300 - 240 = 60 feet leftover to cover at 3 feet/sec

Time taken to cover 60 feet = 60/3 = 20 sec

Average Speed = Total Distance/Total Time = 300/(40 + 20) = 5 feet/sec

Answer (E)

Bill and the group start at 180 feet.

Time taken to meet = initial distance/difference of speeds

\(\frac{180}{6-3}\) = 60 sec

What I assumed here is that in this 60 sec Bill will complete the 300 distance.

Thus, I divided the total distance by total time.

=\(\frac{300}{60}\)

=5ft/sec

What, that I am assuming, is wrong? Is the way I got the answer wrong?