Question

A woman launches a boat from one shore of a straight river and wants to land at the point directly on the opposite shore. If the speed of the boat is 10 mph and the river is flowing east at 5mph, in what direction should she head the boat in order to arrive at the desired landing point

Answer 1

If she stands on the North side of a river flowing to the East at 5 mph,

she must head towards the SouthWest to arrive on the South side of the river directly across from her starting point and we have

x^2 + 5^2 = 10^2 where x is her speed directly across the river

x = (75)^1/2 = 8.66 mph towards the South

sin theta = 5 / 10 = 1/2

She must angle the boat at 30 deg from straight South