Riddle

[spudlyff8fan]

Let's say I've got 12 Gold Coins, and they all look the same, but one weighs a different amount. You go to the local (old time, Libra-style) scale-owner, and you decide to weigh them to figure out which is different. He says you can use his scale, but only 3 times. How can you sure-fire find out which is different?

 

[BCampbell]

The first time, weigh six on one side, six on the other.

The second time, take the lighter bunch of six, and weigh 3 and 3.

The third time, take the lighter 3 and weigh any two. EIther one is lighter, or they are both the same and the one that you didn't weigh is the lighter one.

Do you dress up in a green jumpsuit with question marks all over it to ask these riddles?

 

[BCampbell]

Oops, Katie pointed out that I assumed the coin was lighter. We really don't know.

I think you'd need to know if the odd coin is lighter or hevaier but I'm not positive. The solution for unknown weight that I can think of would be to divide the 12 coins into 3 sets of 4, but that doesn't necessarily narrow it down unless the two sets of four that you weight are the same (then the odd coin is in the set you didn't weigh). This will solve positively in four weighings.

Katie is working on a solution whereby you first weigh two stacks of six, then swap 3 coins from each. We're not sure if that works yet.

 

[spudlyff8fan]

You don't know if it's heavier or lighter. That's part of the answer.

 

[kwilson]

Well a sure fire way is to punch out the guy with the scale and use it as much as you want. What kind of person limits scale use?

Somehow I don't think this is the answer you want...

 

[BCampbell]

Alright, so I goggled it. It's really complex, and nobody who hasn't seen this before will spend the time to figure it out here. Here's the spoiler, if you're really curious click below... if you want to try to figure it out, DON'T click.

http://home.att.net/~numericana/answer/recreational.htm#weighing

 

[Darth_Jonas]

How about you set them all on a table and see which one is bigger or smaller than the rest. They're all gold afterall, and would have to have more material in them to make the difference.

Of course the answer you're looking for is not this one.

 

[spudlyff8fan]

they all look the same,

...

 

[Ace]

man, you already said the one weighs a different amount from the onset. Why the hell weigh anything if you already know?

Like: If a rooster lays an egg on a pitched barn roof...what way....