Question

(2) Sheela con row a boat at the rate 4km/h in still water shetakes 8 hrs in going 12km upstream and 12km downstreamifind the speod of stream.​

Answer 1

☯ Let the stream be x km/hr

☯ Speed of upstream is (4 - x) km/hr

☯ Speed of downstream is (4 -x) km/hr

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• ${\blue{\mathfrak{Time\:\leadsto\:{\dfrac{Distance}{Speed}}}}}$

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Therefore,

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$\frak{Given}\begin{cases} & \sf {Time\:taken\:to\:cover\:12\:km\:upstream\:= \frak{12/4\:-\:x}} \\ \ & \sf {Time\:taken\:to\:cover\:12\:km\:downstream\:= \frak{12/x\:+\:4}}\end{cases}$

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$\underline{\bigstar\:\boldsymbol{According \;to \;the\: given \;Question\; :}}$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{\dfrac{48\:+\:48}{16\:-\:x}^{2}}\:=\:8$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{96\:=\:8\:(16\:-\:x}^{2})$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{\dfrac{96}{8}}\:=\:16\:-\:{x}^{2}$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{12\:=\:16\:-\:x}^{2}$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{x}^{2}\:{=\:16\:-\:12}$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{x}^{2}\:=\:4$

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$\:\:\:\:\:\:\::\:\Longrightarrow\sf\:{x\:=\:{\sqrt{4}}}$

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$\:\:\:\:\:\:\::\:\Longrightarrow\:{\underline{\boxed{\frak{\pink{x\:=\:2}}}}}\:\bigstar$

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$\:\therefore\:{\underline{\sf{The\:speed\:of\:the\:stream\:x\:is\:{\textsf{\textbf{2\:km/hr}}}}}}.$

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