Simple Puzzle

[Chris]

You have 9 ?1 coins, one is a fake. The only way you can tell it is a fake is because it is lighter than the rest. You have an old set of balancing scales, but you can only use them twice.

How do you find the fake coin?

[Stuart]

go to a fun fair and the pikeys will tell you the fake one

[-Bruce-]

the fake will say "Early Learning Centre" on it!! 8)

[Potswalker]

what if you leave them in the sun to see which one melts? :o

[General Baxter]

what if you leave them in the sun to see which one melts? :o

funny :lol:

errr i have no idea :roll:

[joeczucha]

Let X be a real and O be a fake, of course you don't actually know which the fake is.

Spilt them into 3 groups:

1 2 3
X X X | X X O | X X X

You weigh group 1 against group 2. If group 1 is lighter then you know the fake is in group 1. If group 2 is lighter then you know the fake is in group 2. If they are exactly the same then you know the fake is in group 3.

You then choose the group which contains the fake and split that into 3 groups:

1 2 3
X | X | O

You weigh coin 1 against coin 2. If coin 1 is lighter then you know that it is the fake. If coin 2 is lighter then you know that it is the fake. If they are exactly the same the you know that the fake is coin 3.

Easy. Next!!

[Potswalker]

says you can only use the scales twice though? :?

[Stuart]

read again, that is twice

[wisewood]

He means this type of scales... and you would be putting group one at one end and group two at the other side :D

http://www.helensantiques.com/Antiques/Collectibles/Collectible14.jpg

[Chris]

Well done Joe. Thats the best I can come up with, sorry lads (and girls)