Correct Answer - Option 2 : 11 ∶ 1
Formula used ∶
speed of boat in still water be u and the speed of stream be v
Speed upstream = (u - v) km / hr
Speed downstream = (u + v) km / hr
Calculations ∶
Time taken to row upstream = \(\frac{{10}}{{{\rm{u}} - {\rm{v}}}}\) hr ---(1)
Time taken to row downstream = \(\frac{{12}}{{{\rm{u}} - {\rm{v}}}}\) hr ---(2)
On equating (1) and (2) and solving, we get
⇒ u ∶ v = 11 ∶ 1
Hence The ratio of speed of boat in still water to the speed of stream is 11 ∶ 1