Think again!

Interested in “seductive math problems for the modern mind”? Every day Jan Nordgreen, a Norwegian living in Bolivia, posts a new puzzle on his elegant and fun blog, Think Again!

Here is a recent challenge:

A party consists of three couples. At the end of the party one of the husbands asks the others how many new acquaintances they made during the evening. Everybody gives a different answer. What did his wife answer?