Speed of a boat in still water is 15 km/h. It goes 30 km upstream and returns back at the same point in 4 hours 30 minutes. Find the speed of the stream.
Let the speed of the stream be x km/h.
It is given that the speed of a boat in still water is 15 km/h.
Now,
Speed of the boat upstream = Speed of the boat in still water − Speed of the stream = (15 − x) km/h
Speed of the boat downstream = Speed of the boat in still water + Speed of the stream = (15 + x) km/h
We know that
Time=Distance/Speed
Time is taken for upstream journey + Time taken for the downstream journey = 4 h 30 min
Since speed can not be negative, therefore, x = 5.
Thus, the speed of the stream is 5 km/h.