A boat travels 18 , km upstream in 6 , hours. | vedclass

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(C) Let the speed of the boat in still water be $x \, km/h$ and the speed of the current be $y \, km/h$.Given that $y = \frac{1}{4}x$.Upstream speed $

Vedclass · Accepted Answer

$3.6$

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(C) Let the speed of the boat in still water be $x \, km/h$ and the speed of the current be $y \, km/h$.Given that $y = \frac{1}{4}x$.Upstream speed $= x - y = x - \frac{1}{4}x = \frac{3}{4}x$.Time taken to travel $18 \, km$ upstream is $6 \, hours$,so $\frac{18}{\frac{3}{4}x} = 6$.$18 = 6 	imes \frac{3}{4}x \Rightarrow 18 = \frac{18}{4}x \Rightarrow x = 4 \, km/h$.Thus,the speed of the current $y = \frac{1}{4} 	imes 4 = 1 \, km/h$.Downstream speed $= x + y = 4 + 1 = 5 \, km/h$.Time taken to cover $18 \, km$ downstream $= \frac{18}{5} = 3.6 \, hours$.

$A$ boat travels $18 \, km$ upstream in $6 \, hours$. How long (in $hours$) will it take to cover the same distance downstream if the speed of the current is one-fourth the speed of the boat in still water?

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