A boat moves at a rate of 14mph in still water. If the river's current flows at a rate of 5 mph, how long does it take the boat to travel 35 miles upstream?
The speed of the boat upstream =14 - 5 =9 mph Distance =Speed x Time 35 =9 x T T =35 / 9 T =3 8/9 - hours - or about 3 hours and 53 1/3 minutes.
Yes, when it goes upstream you have to subtract, but, if it is heading downstream, then you have to add!
