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.

Question 847766: 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 by ankor@dixie-net.com(22740) (Show Source): You can put this solution on YOUR website!
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.
:
let s = boat speed in still water
then
(s+6) = effetive speed downstream
(s-6) = effective speed upstream
:
Write a distance equation; dist = time * effective speed
Dist up = dist back
3(s+6) = 5(s-6)
3s + 18 = 5s - 30
18 + 30 = 5s - 3s
48 = 2s
s = 48/2
s = 24 km/hr in still water
:
:
Confirm this by finding the actual distances:
3 * 30 = 90
5 * 18 = 90

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