A logician vacationing in the South Seas finds himself on an island inhabited by the two proverbial tribes of liars and truth-tellers.

Members of one tribe always tell the truth; members of the other always lie.

He comes to a fork in the road and has to ask a native bystander which branch he should take to reach a village.

He has no way of telling whether the native is a truth-teller or a liar.

The logician thinks a moment, then asks one question only.

From the reply he knows which road to take.

What question does he ask?

Three boxes - one containing two black marbles, one containing two white marbles, the third containing one black marble and one white marble - are put before you.

The boxes are labeled to indicate their contents - BB, WW and BW - but you are told that the tops have been switched so that every box is now incorrectly labeled.

You are asked to take one marble at a time out of any box, without looking inside, and, using this sampling process, to determine the contents of all three boxes.

What is the smallest number of drawings you will need to determine the contents of each box?

 
The First Prize in the second of this year’s competitions goes to Mr. Arthur Robinson, whose witty entry was easily the best of those we received. His choice of what he would like to read on opening his paper was headed ‘Our Second Competition’ and was as follows:

"The First Prize in the second of this year’s competitions goes to Mr. Arthur Robinson, whose witty entry was easily the best of those we received. His choice of what he would like to read on opening his paper was headed 'Our Second Competition,' but owing to space restrictions we cannot print all of it."

- From Vicious Circles and Infinity: An Anthology of Paradoxes, Patrick Hughes and George Brecht, Penguin Books, NY, 1979