Question

a boat travels 30km up in a river in the same time as it takes to travel 50 km down the same river

Answer 1

Solution :
Let speed of boat in still water = x km/h
Speed of the boat downstream = x + 5
Speed of the boat upstream = x - 5
Speed = Distance / time
So time = Distance / speed
Time taken by boat to travel 30 km upstream = 30/ (x – 5)
Time taken by boat to travel 50 km downstream = 50/ (x + 5)
Since time taken by the boat in both cases is the same ,



=> 30 (x + 5) = 50 (x -5)
=> 30 x +150 = 50x -250
=> 20x = 400
=> x = 20
Thus the speed of the boat in still water is 20 km/h.