Problema Solution
A motorboat took 3 hours to make a downstream trip with a 6km/h current. The return trip against the same current took 5 hours. Find the speed of the boat in still water.
Answer provided by our tutors
let
v = the speed of the boat in still water (no current)
c = 6 km/h the water's current
t1 = 5 h the upstream trip
t2 = 3 h the downstream trip
the speed upstream is: v - c = v - 6
the speed downstream is: v + c = v + 6
since speed = distance/time => distance = time*speed
t1(v - c) = t2(v + c)
5(v - 6) = 3(v + 6)
by solving we find
v = 24 km/h
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the speed of the boat in still water is 24 km/h.