John his wife and their daughter wish to cross a river The row boat can only hold 100 kilos John weighs 80 kilow His wife and daughter each weigh 40 kilos How do all three cross the river?

To get all three across the river using the boat, John can first row across alone, leaving the wife and daughter on the initial side. He then returns alone, picks up his daughter (who weighs 40 kilos), and rows across again. After leaving his daughter on the other side, he returns alone once more and finally takes his wife across. This way, all three safely cross the river without exceeding the boat's weight limit.