Question

A man can swim at 4 ft / s in still water. He wishes to cross the 40-ft-wide river to point B, 30 ft downstream. The river flows with a velocity of 2 ft / s. Note: While in the water he must not direct himself toward point B to reach this point.

Answer 1

Answer:  His swimming forward speed relative to the river is 4ft/s + 2ft/s = 6ft/s

∴  Velocity when swimming across = 40/6 = 6.67ft/s

Explanation:

Since the man is swimming in the same relative speed with the flow of the river, their speed is additional. Also, as he is not swimming toward point B, the distance 30 ft is not inclusive.