Once upon a time there was a beautiful princess named Anna. Anna's father, the King, wanted to be sure his daughter married an intelligent man. To test his daughter's suitors the King hid Anna's picture in one of three boxes. The suitor had to be able to select the box with Anna's picture on one try and within twenty seconds.
On the gold box was the message "Anna's picture is in this box".
The silver box had the message "Anna's picture is not in this box."
"Anna's picture is not in the gold box" was written on the bronze box.
The King would tell each suitor "Only one of the three messages is correct." Which box contained Anna's picture?
The silver box contained Anna's picture. If her picture had been in the gold box, two statements would have been true. (The messages on both the gold box and the silver box.)
If her picture had been in the bronze box, two statements would have been true. (The messages on the bronze box and the silver box.)