kp1811 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?
3.75feet per second?
total distance is 300 feets
120 feet is covered at a speed of (Bills' speed + Belt Speed) = (3+3) = 6feet/sec. Time taken 20sec
remaining 180 feet is covered at a speed of (Bills' speed + Belt Speed) = (0+3) = 3feet/sec. Time taken 60sec
so total time taken to cover 300 foot long walkway is 80 sec. Avg Speed = 300/80 = 3.75 feet/sec
I could be wrong, but the average of 2 average speeds is not the average speed of the entire journey.
Let's take a man cycling 60 miles to work, at 10 miles/hour there and 15 miles/hour back.
The average of the two average speeds will be 12.5 miles/hour
However, the computed average speed is total dist over total time.
If he cycles 10 miles/hour there, he will take 6 hours, and at 15 miles/hour back he will take 4 hours.
120miles/10 hours = 12 miles/hour
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Although I believe weighted average could be used to compute average speed.
But you would need to know time travelled at each speed.
((AverageSpeed1*Time@Speed1) + (AverageSpeed2*Time@Speed2) / (TotalTime)
=((6*10)+(4*15)) / 10