Problema Solution
a boat travels 6 km upstream and 6 km back. the time for the round trip is 2 hrs. the speed of the stream is 3km/hr. what is the speed of the boat in still water?
Answer provided by our tutors
let
v = the speed of the boat in still water
s = 3 km/hr the speed of the stream
d = 6 km the distance traveled in one direction
t = time of the travel downstream (with the current)
2 - t = the time of the return trip upstream (against the current)
the canoe's speed downstream: v + s
the canoe's speed upstream: v - s
since speed = distance/time => distance = speed*time
traveling downstream
(v + s)t = d
(v + 3)t = 6
t = 6/(v + 3)
traveling upstream
(v - s)(2 - t) = d
(v - 3)(2 - t) = 6
plug t = 6/(v + 3) into the last equation
(v - 3)(2 - 6/(v + 3)) = 6
we find
v = 7.24 km/hr
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the speed of the boat in still water is 7.24 km/hr.