Question

A motorboat whose speed in still water is 18 km/h, takes 1 hour more to go 24 km upstream than to return downstream to the same spot. Find the speed of the stream.

Answer 1

Solution:
Let speed of stream = x km/h
Speed of boat in still water = 18 km/h

Speed of boat in upstream = (18 –x )km/h
Speed of boat in downstream = (18 + x ) km/h
Distance = 24 km
As per question, it takes 1 hour more to go upstream 24 km, than downstream

24 km /(18 –x ) = 24 km/(18 + x ) + 1
x² + 48x – 324 = 0
x = 6 or x = – 54

But, as speed can not be negative
Hence, the speed of stream = 6 km/h