Paige jumped into the Savannah River to rescue her dog, Lance.

Question

She was travelling with the current at 8 m/s when she realized that Lance was actually upstream. She turned around and started swimming at the same rate against the current and traveled at 3 m/s. How fast is the current moving? How fast would she be swimming without any current?

Answer 1

Paige is exerting the same amount of force upstream and downstream, so the difference in swimming speeds must come solely from the current. She was traveling 5 m/s faster downstream than upstream (8 - 3 = 5), so the current is moving at 5/2 = 2.5 m/s.

 

That way, Paige, who is swimming at a rate of 5.5 m/s, winds up moving 5.5 + 2.5 = 8 m/s downstream and 5.5 - 2.5 = 3 m/s upstream.