**mdl**

Not sure if it's been answered, but didn't want to scroll through and ruin possible answers to other riddles!

Randomly separate the balls into three groups of three, say groups A, B, and C. Compare groups A and B on the balance scale. If they weigh the same, then the heavier ball is in group C. Otherwise, you the heavier group of three contains the heavier ball. Say the group with the heavier ball is group A. Now choose two balls randomly from group A. Compare them on the balance scale. Either one is heavier than the other and you've found the heavier ball, or they weigh the same, and the heavier ball is the one ball you left out.

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**New Riddle:**

**You are given 99 coins that are heads up, and an unknown number of coins that are tails up. You are blindfolded and somehow can't feel the difference between the heads and tails sides of the coins. You can count the coins, put them in arbitrary many piles, flip whichever coins you want, but remember, when you flip and when you sort, you DO NOT know which ones are heads up, which are tails up. In the end, you must end up with just two piles, each containing an equal number of heads. How do you do this?**

Sorry to be a spoiler, but if you give up here is the answer: Pai's is correct.

http://classic-puzzles.blogspot.com/2006/12/microsoft-puzzle-coins-on-table.html