I found this in the stretch and challenge section of my textbook and I have no clue how to do it! A family cruising upstream on a river (against the river flow) pass a bridge at point A where they drop their sandwich box... they do not notice this for ten minutes until they are at point b where they turn (no time wasted) and pick up the sandwich box at point C. C is 1km away from point the bridge i.e. point A. Calculate the velocity of the river assuming the boat has the same velocity relative to the water up and downstream.
Apparently you do not need to know the velocity of the boat but you DO need to set up equations to calculate the time taken to catch up with the sandwich box
rep to best answer definitely!!!!