Answer:
13 km/h for 65 km
9 km/h for the next 27 km
Explanation:
Velocity of canoe =x km/h for 65 km
Velocity of canoe =x-4 km/h for 27 km after covering 65 km
Total time taken = 9 hours
So,
[tex]\frac{65}{x}+\frac{27}{x-4}=8\\\Rightarrow \frac{65(x-4)+27x}{x^2-4x}=8\\\Rightarrow \frac{92x-260}{8}=x^2-4x\\\Rightarrow 11.5x-32.5=x^2-4x\\\Rightarrow x^2-15.5x+32.5=0[/tex]
Solving this quadratic equation we get,
[tex]x=\frac{15.5\pm \sqrt{240.25+130}}{2}=13\ or\ 2.5[/tex]
Speed cannot be 2.5 as the speed will become negative for the 27 km stretch.
So, velocity of canoe is 13 km/h for 65 km and 9 km/h for the next 27 km