A man can row down stream a distance of 9 km in 2 hours and takes 6 hours while returning to the starting point. What is the speed (in km/h) of the stream?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3 i.e. 1.5.
Let speed in downstream and upstream be D and U
Relative speed when going downstream = Speed of boat + Speed of stream
Relative speed when going upstream = Speed of boat + Speed of stream
D = 9/2 = 4.5, U = 9/6 = 1.5
The speed (in km/h) of the stream = (D - U)/2 = (4.5 - 1.5)/2 = 3/2 = 1.5 km/h