Answer: 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 =[tex]d=speed*time=2(6-x)[/tex]....(1)
Speed in downstream = 6+x
Time taken in downstream = 40 minutes =[tex]=\frac{40}{60}[/tex]hour= 2/3 hour
Distance covered downstream =[tex]d=speed*time=\frac{2}{3}(6+x)[/tex].....(1)
From (1) and (2), we have
[tex]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[/tex]
Hence, The speed of the river current = 3mph
