I’ve always enjoyed this one. My students usually fight over the correct answer.
Three men go to rent a room. The room is $30. Each man pays with a ten dollar bill.
An hour later, the inn-keeper realizes he has over charged by $5. He gives the bell hop five one dollar bills and sends him up to give back the money.
The bell hop figures a tip is in order so he puts two of the dollars in his shirt pocket and gives each of the men a dollar each.
So…each man paid nine dollars (they each got one back). Three times nine is 27. The bell hop has two bills in his shirt. That’s 29. Where’s the 30th dollar?
Answer: you’re counting the bellhop’s money twice, and the money in the men’s pockets not at all. The bellhop’s $2 is part of the $27 that the three men paid. So there’s not one dollar missing, there’s 3. And where are those $3? In the men’s pockets.
Riddle 1
Be you ever so quick with your vision keen.
By your eyes we are never seen.
Unless perchance it should come to pass.
You see our reflection in a looking glass.
Oldie but a goodie. Given 12 identical looking coins. One coin is counterfeit. The eleven authentic coins weigh exactly the same. The counterfeit coin weighs either more or less than than the other eleven coins. With only three weighings, can you determine which coin is counterfeit, and if it weighs more or less than the authentic coins?
Clue: Here’s a little help… I was in a bar working on this puzzle with a friend one night, when the waitress wanted to help solve the puzzle, so she asked: “What denomination are the coins?”. Your clue for the day is - IT DOESN’T MATTER WHAT DENOMINATION THE COINS ARE! I was so disappointed to find that the rumors about girls from the Jersey Shore were true. Nice looking, but oh so dumb.
I don’t see how Pete’s answer satisfies the coin riddle. The only thing that weighing three groups of four would do is tell you in which quartet the counterfeit coin is to be found. It doesn’t, however, identify which of the four is the fake.
Enright3: I need a little clarification on your riddle: are we to weigh the coins using a scale, or with an old-fashioned balance? If it is a balance, I can find the culprit coin in three weighings – but only if I know from the start whether the bogus coin I’m looking for is heavier or lighter than the rest! Damn!
Let me know by which method the coins are supposed to be weighed, and I’ll keep working on it.
~ Complacency is far more dangerous than outrage ~
