Question Detail
A man can row \begin{aligned} 9\frac{1}{3} \end{aligned} kmph in still water and finds that it takes him thrice as much time to row up than as to row, down the same distance in the river. The speed of the current is.
- \begin{aligned} 3\frac{2}{3}kmph \end{aligned}
- \begin{aligned} 4\frac{2}{3}kmph \end{aligned}
- \begin{aligned} 5\frac{2}{3}kmph \end{aligned}
- \begin{aligned} 6\frac{2}{3}kmph \end{aligned}
Answer: Option B
Explanation:
Friends first we should analyse quickly that what we need to calculate and what values we require to get it.
So here we need to get speed of current, for that we will need speed downstream and speed upstream, because we know
Speed of current = 1/2(a-b) [important]
Let the speed upstream = x kmph
Then speed downstream is = 3x kmph [as per question]
\begin{aligned}
\text{speed in still water = } \frac{1}{2}(a+b) \\
=> \frac{1}{2}(3x+x) \\
=> 2x \\
\text{ as per question we know, }\\
2x = 9\frac{1}{3} \\
=> 2x = \frac{28}{3} => x = \frac{14}{3} \\
\end{aligned}
So,
Speed upstream = 14/3 km/hr, Speed downstream 14 km/hr.
Speed of the current \begin{aligned} =\frac{1}{2}[14 - \frac{14}{3}]\\
= \frac{14}{3}
= 4 \frac{2}{3} kmph \end{aligned}
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Chandan Sadhukhan 6 years ago
I can't understand the clear language of the question no 6.
It would be better if I get it in English
Videos @mastguru
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