Posted by Kara on Monday, June 7, 2010 at 8:48pm.
Let V = stream velocity and v = boat velocity with respect to water. Both are in km/hr.
3 hr = 30/(V + v)
5 = 30/(V -v)
Solve those two equations in two unknowns for V and v.
5(V -v) = 3(V +v)
2V = 8v
v = V/4
3 = 30/(5V/4)= 120/5V
15V = 120
etc
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