T2B25

One of Raymond Smullyan's most famous puzzles includes Portia's Caskets. This set of riddles starts out fairly easy, and gets to the final and most difficult one.

I think that the last puzzle only keeps its difficulty if you do the entire series, so I'll start posting a puzzle a day until I get to the final one.

First Puzzle:

The statements on the gold and lead caskets say the opposite, hence one of them must be true. Since at most one of the three statements is true, then the statement on the silver casket is false, so the portrait is actually in the silver casket.
This problem could be alternatively solved by the fol­ lowing method: If the portrait were in the gold casket, we would have two true statements (namely on the gold and lead caskets), which is contrary to what is given. If the portrait were in the lead casket, we would again have two true statements (this time on the lead and silver caskets). Therefore the portrait must be in the silver casket.
Both methods are correct, and this illustrates the fact that in many problems there can be several correct ways of arriving at the same conclusion.

First Answer:

In Shakespeare's Merchant of Venice Portia had three caskets-gold, silver, and lead-inside one of which was Portia's portrait. The suitor was to choose one of the caskets, and if he was lucky enough (or wise enough) to choose the one with the portrait, then he could claim Portia as his bride. On the lid of each casket was an inscription to help the suitor choose wisely.
Now, suppose Portia wished to choose her husband not on the basis of virtue, but simply on the basis of in­ telligence. She had the following inscriptions put on the caskets.

Gold
THE PORTRAIT IS IN THIS CASKET

Silver
THE PORTRAIT IS NOT IN THIS CASKET

Lead
THE PORTRAIT IS NOT IN THE GOLD CASKET

Portia explained to the suitor that of the three statements, at most one was true.

Which casket should the suitor choose? 

Tomorrow, puzzle number 2...