Solution: The speed of a boat in still water is v. The boat is to make a round trip in a river whose current travels at speed exttip{u}{u}.Derive a formula for the time needed to make a round trip of total distance exttip{D}{D} if the boat makes the round trip by moving upstream and back downstream.Derive a formula for the time needed to make a round trip of total distance exttip{D}{D} if the boat makes the round trip by moving directly across the river and back.