Mathematics: Tinh can row at a rate of 6 mph in still water. it takes her 2 hours to row upstream from a dock to a park. she then rows back to the dock, and it only takes 40 minutes. what is the speed of the river current?

Tinh can row at a rate of 6 mph in still water. it

Ответ:

thefish81

01.01.2022

Mathematics

The speed of the river current = 3mph

Step-by-step explanation:

Let x be the speed of the river current.

Given: The speed of Tinh in still water = 6 mph

Let d be the distance from dock to park.

Now, speed in upstream = 6-x

Time taken in upstream = 2 hours

Distance covered upstream = d=speed*time=2(6-x) ....(1)

Speed in downstream = 6+x

Time taken in downstream = 40 minutes = $=\frac{40}{60}$ hour= 2/3 hour

Distance covered downstream = $d=speed*time=\frac{2}{3}(6+x)$ .....(1)

From (1) and (2), we have

$2(6-x)=\frac{2}{3}(6+x)\\\Rightarrow\ (6-x)=\frac{1}{3}(6+x)\\\Rightarrow\ 3(6-x)=6+x\\\Rightarrow\ 18-3x=6+x\\\Rightarrow\ x+3x=18-6\\\Rightarrow\ 4x=12\\\Rightarrow x=3$

Hence, The speed of the river current = 3mph

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Tinh can row at a rate of 6 mph in still water. it takes her 2 hours to row upstream from a dock to a park. she then rows back to the dock, and it only takes 40 minutes. what is the speed of the river current?

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