Question

A boat is traveling in a river with a current that has a speed of 1.5 km/h. In one hour, the boat can travel twice the distance downstream as it can travel upstream. How long will it take the boat to travel 100 km in still water?

Answer 1

If the still-water speed is s, then since distance = speed*time, then in equal time (say, t=1),

(s+1.5) = 2(s-1.5)
s+1.5 = 2s-3
s = 4.5

100/4.5 = 22.22 hrs
or 22 hr 13 min 20 sec