A boat moves at a rate of 10 mph in still water. If the river's current flows at a rate of 3 mph, how long does it take the boat to travel 22 miles upstream?
The current is against you, so your effective rate is 10 - 3 = 7 mph
So
Distance / Rate = Time
22 / 7 = Time = about 3 + 1/7 hours
