Speed of a man in still water is (28/3) km/h. It takes him thrice as much time to row upstream as it takes to row downstream. What is the velocity of the stream?

Correct option is D

Given:
Speed of man in still water = (28/3) km/h Time taken upstream = 3 * Time taken downstream
Formula Used:
Let the speed of the stream be x km/h. Speed downstream = Speed in still water + Speed of stream Speed upstream = Speed in still water - Speed of stream
Solution:
Let the velocity of the stream is x and the distance = d
Speed of man in still water = 28/3
Speed of man in upstream = 28/3-x
Speed of man in downstream = 28/3+x
As per the question,
(d/(28/3-x))=3(d/(28/3+x))
(d/((28-3x)/3))=3(d/((28+3x)/3))
(3d/(28-3x))=3(3d/(28+3x))
1/(28-3x)=3/(28+3x)
84 - 9x = 28 +3 x
12x = 56
x = 14/3.