The current in a river is 10 mph. A boat can travel 50 mph in still water. How far up the river can the boat travel if the round trip is to take 5 hours? Choose the most appropriate option.
A) 120
B) 100
C) 96
D) 85
E) 150

Rationale: upstream speed = 50 - 10 = 40 mph downstream speed = 50 + 10 = 60 mph d / 40 + d / 60 = 5 hours solving for d we get d = 120 answer : a
Answer: A