People seem to like the brain teasers I’ve posted. So here’s another.

I first ran across this when I was about 12 years old. I still remember it as one of the toughest brain teasers I ever faced.

It is a very simple problem to explain, but the answer may not be obvious. So take your time and think it through.

**Find the Counterfeit Coin**

You have 12 identical coins. One of them is counterfeit. The counterfeit coin may be heavier or lighter than the others.

Using a simple balance scale, and in just 3 weighings, identify the counterfeit coin, and determine whether it is lighter or heavier than the others.

**The Challenge**

Is it possible to solve this problem?

- If “Yes” then what is the solution?
- If “No” then why is it impossible?

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