Two logicians place cards on their foreheads so that what is written on the card is visible only to the other logician. Consecutive positive integers have been written on the cards. The following conversation ensues:

A: "I don't know my number."

B: "I don't know my number."

A: "I don't know my number."

B: "I don't know my number."

........ n statements of ignorance later..........

A or B: "I know my number."

What is on the card and how does the logician know it?

The puzzle says "n statements of ignorance later" after 4 statements of ignorance have already been made. Does that mean there are n+4 statements of ignorance? The prior comments assume n statements of ignorance in all.

Just nitpicking on my part.

Posted by Charlie on 2003-04-11 08:33:10