posted by ruca on .
A man who can row in still water at 3 mph heads directly across a river flowing at 7 mph.
At what angle to the line on which he is heading does he drift downstream and at what speed does he drift downstream?
He drifts downstream at the river's speed, 7 mph. He has a 3 mph component across the river.
His direction with respect to the heading angle (straight across) is
tan^-1 7/3 = 66.8 degrees (towards downstream)