Respuesta :
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=[tex]\frac{distance}{speed}[/tex]
[tex]6=\frac{4}{5+v}+\frac{4}{5-v}[/tex]
[tex]6=4\left [ \frac{1}{5-v}+\frac{1}{5+v}\right ][/tex]
[tex]1.5=\left [\frac{5+v+5-v}{\left ( 5+v\right )\left (5-v \right )} \right ][/tex]
[tex]75-3v^2=20[/tex]
[tex]v=\sqrt{\frac{55}{3}}\approx 2.5mph[/tex]
