Three friends Pablo, Edvard, and Henri are talking to each other about the art collection of Leonardo. Pablo says: ''Leonardo has at least four paintings of Rembrandt.'' Edvard says: ''No, he has less than four paintings of Rembrandt.'' ''According me,'' says Henri, ''Leonardo has at least one Rembrandt.''
If you know that only one of the three friends is right, how many Rembrandts does Leonardo possess?
Look at the statements about the number of paintings of Rembrandt. If Pablo would be right ("at least four"), then Henri ("at least one") would also be right. If Henri would be right ("at least one"), then or Pablo ("at least four") or Edvard ("less than four") would also be right. This means only Edvard can be right and Leonardo possesses less than one Rembrandt, so no Rembrandt at all.