A person can row 7(¹/₂) km an hour in still water. Finds that it takes twice the time to row upstream than the time to row downstream. The speed of the stream is:

12 kmph
22.5 kmph
33 kmph
44 kmph

Answer:- 1

Explanation:-

Solution:

Let the distance covered be x km and speed of stream = y kmph.
Speed downstream = (¹⁵/₂)+y = kmph
Speed upstream = (¹⁵/₂)-y = kmph

\begin{aligned} According to question, \\ [\frac{2 x}{((\frac{15}{2}) + y)}] = [\frac{x}{((\frac{15}{2}) - y)}] \\ o r, 15 - 2 y = (\frac{15}{2}) + y \\ o r, 3 y = 15 - (\frac{15}{2}) = \frac{15}{2} \\ o r, y = \frac{15}{6} = 2.5 kmph \end{aligned}

$\eqalign{ & {\text{According}}\,{\text{to}}\,{\text{question,}} \cr & \left[ {\frac{{2x}}{{\left( {\left( {\frac{{15}}{2}} \right) + y} \right)}}} \right] = \left[ {\frac{x}{{\left( {\left( {\frac{{15}}{2}} \right) - y} \right)}}} \right] \cr & or,\,15 - 2y = \left( {\frac{{15}}{2}} \right) + y \cr & or,3y = 15 - \left( {\frac{{15}}{2}} \right) = \frac{{15}}{2} \cr & or,y = \frac{{15}}{6} = 2.5\,{\text{kmph}} \cr}$