A person can row a boat at the rate of $5\ km/h$ in still water. He take thrice as much time in going $40/km$ upstream as in going $40/km$ downstream. Find the speed of the stream.

Academic Mathematics NCERT Class 10

Given: A person can row a boat at the rate of $5\ km/h$ in still water. He take thrice as much time in going $40/km$ upstream as in going $40/km$ downstream.

To do: To find the speed of the stream.

Solution:

Let's consider,

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

Speed of stream $=x\ km/hr$

Upstream Speed $=(5−x)\ km/hr$

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

According to the question,

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

$\Rightarrow 5+x=15−3x$

$\Rightarrow 4x=10$

$\Rightarrow x=2.5\ km/hr$

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Updated on: 10-Oct-2022

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