A person, rowing at the rate of $ 5 \mathrm{~km} / \mathrm{h} $ in still water, takes thrice as much time in going $ 40 \mathrm{~km} $ upstream as in going $ 40 \mathrm{~km} $ downstream. Find the speed of the stream.

AcademicMathematicsNCERTClass 10

Given:

A person rowing at the rate of 5 km/h in still water, takes thrice as much time in going 40 km upstream as in going 40 km downstream.

To do:

We have to find the speed of the stream.

Solution: 

Speed of rowing by the person $=5\ km/hr$.

Let the speed of the stream be $x\ km/hr$.

Upstream Speed $=(5−x)\ km/hr$

Downstream speed $=(5+x)\ km/hr$

According to the question,

$\frac{40}{5−x}=\frac{3\times40}{5+x}$

​$\Rightarrow 5+x=15−3x$

$\Rightarrow 4x=10$

$\Rightarrow x=2.5\ km/hr$

Therefore, the speed of the stream is $2.5\ km/hr$.

raja
Updated on 10-Oct-2022 13:27:24

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