A motorboat going downstream overcame a raft at a point A. One hour later it turned back and after sometime passed the raft at a distance 12 km from the point A. Find the river velocity (in km/hr) assuming the speed of the motorboat to be constant.
Jobs | Jobs | Jobs | |
Machines | I | II | III |
$$M_1$$ | $$1$$ | $$4$$ | $$5$$ |
$$M_2$$ | $$4$$ | $$2$$ | $$7$$ |
$$M_3$$ | $$7$$ | $$8$$ | $$3$$ |