Please help. WInd and Water Current Problem

Question

Suppose you can paddle a canoe in still water at 5 km/h and that you are going to travel 6km up a river and 6km back. If the river current is 1km/h, find your total time and average speed for the round trip.

Answer 1

Part 1 - upstream    distance = rate x time

distance = 6km; rate = still water speed less current = 5km/h - 1km/h = 4km/h

distance ÷ rate= time; 6km ÷ 4km/h = 1.5h

 

Part 2 - downstream   distance = rate x time

distance = 6km; rate = still water speed plus current = 5km/h + 1km/h = 6km/h

distance ÷ rate = time; 6km ÷ 6km/h = 1h

 

Part 3 - total time =  1.5h + 1h= 2.5h

 

Part 4 - average speed  distance = rate x time; r = d ÷ t 

distance = upstream + downstream = 6km + 6km = 12km

time = 2.5h; 12km ÷ 2.5h = 4.8km/h average speed