SPEED TIME DIST.
UPSTR 20-c t 60
DOWNSTR 20+c t 100
Value of is equal both to and to , so meaning .
Simplify and solve for c.
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Same type exercise comes up too often.
Something moves upstream for U distance in the same time as it moves D distance downstream. The craft or vehicle normally moves at R speed in absence of stream or river current.
What is the speed of the current?
SPEED TIME DIST.
UPSTR R-c U/(R-c) U
DOWNSTR R+c D/(R+c) D