A boy wants to cross a river from south to north: he can’t swim, there aren’t any boats available, and the only bridge across the river is watched over by a guard who comes out of his hut every five minutes. It is impossible to cross the bridge in less than 10 minutes. How do you think the boy will cross the river?



A.  He walked across from south to north. As the guard emerged from his hut, the boy turned around and pretended he was walking from north to south. The guard then ran after him and shooed the back the way he though he had come- that is the north side of the river.