Question

A steamer, going downstream in a river, covers the distance between two towns in 20 hours. Coming back,
upstream, it cover this distance in 25 hours. The speed of water is 4 km/hr. Find the distance between the two
towns?​

Answer 1

Let s = speed of the boat in still water

then

(s-4) = speed upstream

and

(s+4) = speed downstream

;

Distance both ways is equal. Make a distance equation; Distance = Time * speed

Up distance = down distance

25(s-4)= 20(s+4)

:

25s - 100 = 20s + 80

25s - 20s = +100 + 80

5s = 180

s = 180/5

s = 36 mph

:

Find the distance:

Dist = time * speed

downstream: d = 20(36+4) = 800 mi

and

Upstream: d = 25(36-4) = 800 mi also