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Kinetic graphs - class-X
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A man rows to a place 48 km distant and comes back in 14 hours. He finds that he can row 4 km with the stream in the same time as 3 km against the stream. The rate of the stream is ............
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A
1 km/hr
💡 Explanation:
Suppose he move 4 Km downstream in x hours.Then
Speed downstream=$\frac{4}{n}$Km\hr
Speed upstream=$\frac{3}{n}$Km\hr
$\therefore \frac{48}{$\frac{4}{n}$}+\frac{48}{\frac{3}{x}}=14$
$\frac{48x}{4}+\frac{48x}{3}=14$
Or x=$\frac{336}{168}=2$
So spead downstream=$\frac{4}{\frac{1}{2}}=8$Km\hr
Or speed upstream =$\frac{3}{\frac{1}{2}}=6$Km\hr
So rate of stream =$\frac{1}{2}(8-6)=\frac{2}{2}=1$Km\hr