A man can swim in still water at a speed of 6 km/h, but he takes thrice as long to swim upstream as downstream. The speed of the man, when swimming downstream is :
Answer & explanation
Correct answer: option 3
Let the speed of the river = a km/h
Speed of man during upstream = 6 - a
Speed of man during downstream = 6 + a
Let the distance be X km
Time taken in the upstream = 3 × (Time taken in the downstream)
\(\frac{X }{6 - a }\) = \(\frac{3X }{6 +a }\)
3(6-x) = (6 + x )
18 - 3x = 6 + x
12 = 4x
x = 3 km/h
So speed of man in downstream = 6 + 3 = 9 km/h