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  • A boat covers a certain distance downstream in 1 hour, while it comes back in 1  hours. If the

A boat covers a certain distance downstream in 1 hour, while it comes back in 1  hours. If the speed of the stream be 3 kmph, what is the speed of the boat in still water?

 

  • Option 1)

     

    12 kmph

     

  • Option 2)

     

    13 kmph

     

  • Option 3)

     

    17 kmph

     

  • Option 4)

     

    15 kmph

     

  • Option 5)

     

    14 kmph

Answers (1)

best_answer

Assuming you meant the return (upstream) time is $11 / 2$ hours:
Let the speed in still water be $b \mathrm{~km} / \mathrm{h}$ and stream speed $s=3 \mathrm{~km} / \mathrm{h}$.
Distance $D$ is the same both ways.
- Downstream: $D=(b+3) \times 1=b+3$
- Upstream: $D=(b-3) \times 1.5=1.5(b-3)$

Equate:

$
\begin{gathered}
b+3=1.5(b-3)=1.5 b-4.5 \\
7.5=0.5 b \Rightarrow b=15
\end{gathered}
$
Speed of the boat in still water $=15 \mathrm{~km} / \mathrm{h}$.

Posted by

rishi.raj

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