water flows in river 0.5km wide with speed 6km/hr. A boat can travel with speed 10km/hr in still water. In what direction should boat sail to reach opposite bank?

Answer 1

draw the figure. right triangle, hypotenuse 10, opposite side 6.

theta upstream=arcsin6/10

Answer 2

Vc + Vb = 6 + 10i = 11.7km/h[59o] CCW. = 31o E. of N.

Boat should sail 31o W. of N.

Answer 3

Vb - 6i = 10,
Vb = 10 + 6i = 11.7 km/h[31o] CCW = 31o N. of E.