A fisherman travels downstream at full speed to his favorite fishing spot. The stream is running at a rate of 5 miles per hour, and the trip takes 2 hours to get to the fishing hole. He is surprised, however, to find that the trip takes 6 hours at full speed to get back to the dock when he is finished. How fast will his fishing boat go?

Question

ankit042 · Answer

Let us assume the speed of boat be x miles per hour.

For the case of downstream actual speed will be x+5 miles per hour
Distance travelled for downstream = 2*(x+5)

Effective speed when going upstream will be x-5
Distance for upstream = 6*(x-5)
 Because two distances are equal we get the equation
2*(x+5) = 6*(x-5)
2x+10 =  6x-30
40 = 4x
x = 10 miles per hour