A TED-Ed lesson by Lisa Winer explains how to solve the river crossing riddle, but also lays out the steps to solve variations of the riddle using logic. In the example, three lions and three wildebeests need to cross a river using one raft, but at no time can the lions outnumber the wildebeests.
As a wildfire rages through the grasslands, three lions and three wildebeest flee for their lives. To escape the inferno, they must cross over to the left bank of a crocodile-infested river. Can you help them figure out how to get across on the one raft available without losing any lives?