1. The problem statement, all variables and given/known data A boat takes 2.80 hours to travel 30.0 km down a river, then 4.50 hours to return. How fast is the river flowing 2. Relevant equations Vac = Vab + Vbc 3. The attempt at a solution I wasn't quite sure how to use the formula that the professor gave us which is above for this particular problem. The way I see it, since the problem doesn't say their is a change in acceleration, I'm thinking the speed of the boat IS the speed of the river seeing as it is saying "down" a river..... so I just took 30 / 2.8 which gives me the speed of the boat but.... It's not the answer.