Question

Explain in paper


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Answer 1

Speed in still water = Average of speed in down and upstream.

Speed in still water = $\dfrac{12 + 6}{2}$

Speed in still water = $\cancel\dfrac{18}{2}$

Speed in still water = $\underline{9\:Km/h}$

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Therefore correct option is $\Large\boxed{\red{(3)\:9\:km/hour}}$