A man is rowing a boat at 9km/h in the river 1.5km wide in which current is 5km/h.in which direction should he head in order to get across the river in the shortest possible time? how much time will it take?

Answer 1

he wants to cross straight over, so he needs to head upstream at an angle x, where
sinx = 5/9
That makes his speed across 7.48 km/hr
So, how long will it take to cover the 1.5 km?

Answer 2

a. Vb - 5i = 9.
Vb = 9 + 5i = 10.3km/h[29.1o] N. of E. = Velocity of boat.

b. d = V*t = 1.5.
9 * t = 1.5,
t = 0.166h = 10 min.