Charlie rides his bicycle down a hill at 30 kilometers per hour. Then he turns around and rides back up the hill at 6 kilometers per hour to his starting point. What is Charlie's average speed for the whole trip down and back up the hill?

Guest Jun 26, 2020

#1**+1 **

The distance is the same d = rate * time it is the TIME that is different

d = 30 k/h * t1

d = 6k/h * t2 and they are equal

d/30 = t1 and d/6 =t2

Total distance is 2 d

2d = Average *(t1 +t2)

2d = average * (d/30 + d/6)

2d = average ( (d+5d)/30)

2d = average * (6d/30)

2d * 30/6d = average

2*30/6 = average = 10 k/hr

ElectricPavlov Jun 26, 2020