Angle ABC is an inscribed angle and its angle equals one half of the intercepted arc.
Angle ABC = 118 / 2 = 59 degrees.
Source:
http://www.1728.org/circangl.htm
We calculate both velocities:
upstream 8 miles in 2 hours = 4 miles / hour
downstream 8 miles in 1 hour = 8 miles / hour
ps -stream speed = 4 mph
ps + stream speed = 8 mph
Adding both equations
2 ps = 12 mph
paddling speed = 6 mph
stream speed = 2 mph
