A group of k villagers must cross, the Sarawak river, which is a wide and deep river. There is no bridge in sight. They notice two 10-year-old boys playing in a rowboat at the shore. The boat is so tiny and it can hold only two boys or one villager. How can the villagers can get across the river and leave the boys in joint possession of the boat? How many times the boat pass from shore to shore? [Hint: Solve the problem by starting with k = 1]

2 answers

Assume the boat and the boys are on the same side of the river at the start and finish.

To get one villager across, the two boys must row over, leave a boy on the other side, row back alone, let a villager row over, then then boy on the other side will bring the boat back, completing one cycle. The two boys are on the initial side of the river.

So it takes two return trips for one villager to get over.
But the question above state that a group of k villagers. can we assume that only 1 villager row over?