5.A boat travelling at top speed upstream moves at 15 km/hr. When it travels downstream, again at top speed, it moves at 25 km/hr. What is the boat’s top speed in still water?

10 ! a train starts from grand city and travels toward belleville 388 miles away. at the same time, a train starts from belleville and runs at the rate of 47 miles per hour toward grand city. they pass each other 4 hours later. find the rate of the train from grand city.