Question

Roy kayaked up the river and then back in a total time of 6 hours. The trip was 4 miles each way, and the current was difficult. If Roy kayaked at a speed of 5 mph, what was the speed of the current? Round your answer to the nearest tenth.

Answer 1

Answer:2.5 mph

Explanation:

Total time for trip=6 hr

Speed of roy=5 mph

the trip 4 miles one side

Let v be the stream velocity

time=$\frac{distance}{speed}$

$6=\frac{4}{5+v}+\frac{4}{5-v}$

$6=4\left [ \frac{1}{5-v}+\frac{1}{5+v}\right ]$

$1.5=\left [\frac{5+v+5-v}{\left ( 5+v\right )\left (5-v \right )} \right ]$

$75-3v^2=20$

$v=\sqrt{\frac{55}{3}}\approx 2.5mph$

Answer 2

Just had this question on my quiz, the answer ended up being 4.3 mph