Three couples

Here is a crossing puzzle similar to Cannibals and missionaries. I first saw this in Averbach and Chein.

Puzzle

Three couples are on a safari, when they come to a river. The only way for them to cross is with a small rowboat which can only accommodate two people at a time. Complicating the process is the fact that the women are all the jealous type, and refuse to leave their significant other in the presence pf another woman unless she is there as well. How can the couples cross the river without any romantic strife?

Variations

On the way back, two extra couples have joined the group. Luckily, the boat has been upgraded and can now accommodate three passengers at a time. Sadly, the wives are just as suspicious as before. How can the group cross?

In another presentation of this puzzle, the couples are replaced by pairs of knights and pages. Any page left in the company of another knight, without his own knight to protect him, would either be killed or would die of fright.

See also

Cannibals and missionaries

Farmer and the boat

Four travelers

References

Problem Solving Through Recreational Mathematics by Bonnie Averbach and Orin Chein.