Joan A. answered • 03/12/15

Retired professional specializing in Math, Science, and English

You need to know whether Treveon's paddle speed downstream is the same as Mark's upstream.

Mark's net upstream speed was 13mi/10 hr = 1.3 miles per hr. To overcome the speed of the water current, he would need to paddle at 4 mph + 1.3 mph = 5.3 mph.

If Treveon is paddling at the same 5.3 mph then the downstream speed is the paddle speed plus the water current speed 5.3 mph + 4 mph = 9.3 mph. To go 13 miles, it would take 13 miles/9.3 mph or approx. 1.4 hours