## Tuesday, December 11, 2007

### Blind coin-sorting

Difficulty: 4 of 10

I pull out a stack of pennies. I use pennies because I don't trust you. Last time, you stole a quarter. I know you did! I counted. You wonder where I got a stack of pennies, and what kind of person still carries around such worthless things. But before you can ask, I produce an ugly green and blue handkerchief and say, "Blindfold yourself." While you blink incredulously at me, I explain: "It's in the name of Reason!" I make sure to capitalize "Reason" as I speak. "Or Fun. Or Whatever Else it is that you like."

After some more incredulous blinking, you finally tie the handkerchief around your head. It smells faintly of skepticism. You hear the clatter of a stack of pennies being scattered on the table. I say, reassuringly,
"Preliminary tests suggest that this is a fun 'party trick,' as they call it." I make quote motions with my fingers as I say "party trick," but you can't see them, which is why I need to type out what I'm doing. You wonder why it is that you are performing the party trick and not I.

I boldly declare,
"There are five tails showing among the pennies on the table! Your task is to sort all of the pennies into two groups, each group showing an equal number of tails!"

I ignore your incredulous blinking, almost as if I could not see through your blindfold. After a bit of hesitation, you pick up a penny, and try to feel whether it is heads or tails. "No!" I shout, surprisingly close to your ears. "There is an easier way, without tricks! Think!" You start to mumble that you feel uncomfortable, but I cut you off with another, "Think!" I go on to reassure you, "If you can't figure it out, don't worry. You'll only be doomed to blindly flip and sort coins until I post the solution in a few days."

<blatant genre switch>
Are you unable to solve the puzzle? Turn to page 2.
</blatant genre switch>

DeralterChemiker said...

A couple of last minute hints, folks. First, the groups need not be equal in size. Second, the number of tails in each group can be anywhere from 0 to 5. But is this puzzle only a 2?? I'm going to feel awfully stupid when you get to 4s and 5s.

miller said...

Maybe I should increase the difficulty. I only think this stuff's easy because I already know the answer.

Anonymous said...

Turn one coin over.
Shuffle the coins around a bit.
Remove the blindfold.
Point at two or three tails and say "There's one group - I deliberately moved them to those locations."
:P

miller said...

Clever, but you're not allowed to remove the blindfold.