The speed of a boat in still water is 50km/h. It takes the same time for the boat to

travel 10km upstream as it does to travel 20km downstream. Find the speed of the

current.

The speed of a boat in still water (b) is 50km/h. It takes the same time (t) for the boat to travel 10km (x) upstream as it does to travel 20km (y) downstream. Find the speed of the current.

upstream speed (u) = speed in still water (b) - stream speed (s) = b-s = 50-s

downstream speed (d) = speed in still water (b) + stream speed (s) = 50+s

time (t) = x/u = y/d

10 / (50-s) = 20 / (50+s)

10 (50+s) = 20 (50-s)

500 + 10s = 1000 - 20s

30s = 500

stream speed (s) = 500/30 = 16.6 km/h