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