OK - slightly harder puzzler.

You have twelve balls (matron!), all the same size and colour. Eleven of them weigh the same, but one of them has a different weight from the other eleven. You don't know if it's heavier or lighter than the rest and you don't know which ball it is. The difference in weight is small enough that you can't tell just by picking them up and seeing how heavy they feel in your hands.

You have a balance beam i.e. you can put one set of balls on one end and another set of balls on the other end and find out if both sets weigh the same or one set is lighter than the other.

What is the minimum number of weighings with which you can absolutely identify both the odd ball out and whether it's lighter or heavier than the rest?

Posted By: Partial Angler on January 27th 2006 at 12:19:42

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