Fifteen Eighty Four

Academic perspectives from Cambridge University Press


Win a New Martin Gardner Book #4

September 24, 2008

[Update] This week is over! The winner, and the current contest, will be announced here.

Today, we’ll start on the puzzles from Hexaflexagons, Probability Paradoxes, and the Tower of Hanoi. I’ll run three; that’s three more weeks of puzzle goodness.

Incidentally, don’t miss Don Albers’ lengthy interview with Gardner, updated weekly.

Last week: the final puzzle from Origami, Eleusis, and the Soma Cube. Gardner’s puzzle last week saw a bank teller inadvertently doubling a man’s withdrawal, having switched dollar and cent values. Doubling, that is, if one takes into account that pesky five-cent newspaper.

I’ve chosen a winner at random this week:

And the book goes to J. Snyder who, incidentally, correctly identified the equation as:

‘…a linear diophontine equation which is c + d/100 – 5/100 = 2*(d + c/100), where c=cents and d=dollars’

The answer: $31.63

This week’s puzzle (a logic one, for all the philosopher-types out there) after the jump:

Click here for the rules >>

The Fork in the Road

Here’s a recent twist on an old type of logic puzzle. 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 a 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 liar. The logician thinks a moment and then asks one question only. From the reply, he knows which road to take.

What question does he ask?

Gardner discusses the many permutations of this question at length in the book, as well as varied definitions of “Liar”. For our purposes here, we’ll assume that the answer is confined to a single “yes” or “no.”

[Update] Many of the answers seem to assume that there is a village at BOTH branches, or that the logician must differentiate the truth-teller village from the liar village. I know, I know, you’re just stopping through. Read again.

Answer in the form below. Use “Gardner Week 4” in the subject line. If you wish to send an attachment, please email it to:

cupblog (dot) us (at) gmail (dot) com

Some of you have noted that this form has cut off after a line. I’m sorry if it gives any more trouble. If I get any answers that seem to do so, I’ll shoot you an email.

All information will remain confidential.


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