Question

A man on a west side of a river that flows from north to south at 1.17 m/s. He wants to swim across the river from point A and arrive at point B. He can swim at a speed of 1.35 m/s in a pool. If the river is 207 m wide, it will take him how long to reach point B?

Answer 1

$v=\sqrt{1.35^2-1.17^2}=0.67\ (m/s)$

$t=207/0.67\approx309\ (s)=5\ min\ 9\ s$ . Answer