The current in a river is 4 mph. A boat can travel 18 mph in still water. How far up the river can the boat travel if the round trip is to take 10 hours? Pick one
A) 69 miles
B) 85.5 miles
C) 96 miles
D) 100 miles
E) 112 miles
Upstream Speed = 18-4= 
<gadget id="calculator">18-4</gadget>
<output>14</output>
14 mph   Downstream Speed= 18+4= 
<gadget id="calculator">18+4</gadget>
<output>22</output>
22 mph   D/14 + D/22= 10 hours   Solving for D we get D=85.5   Answer: 85.5 miles
<result>B</result>
The current in a river is 4 mph. A boat can travel 18 mph in still water. How far up the river can the boat travel if the round trip is to take 10 hours?