# Coin Quiz

Use lateral thinking.

You have 30 gold coins but one is counterfeit and lighter than a real coin. The only equipment you have is a simple pair of balance scales. What is the least number of weighings necessary to discover the counterfeit coin?

Explain the problem.

Explain the method you used to reach your answer and show working out.

State the answer.

HEHE TRY THIS PEOPLE. =D

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Weighing 1. 15 coins per side.

One side will be lighter; or the other side will be heavier.

Weighing 2. Split the lighter pile into 2×7 with one over.

If the two piles balance, then the false coin is the one you left out and your weighings are finished.

Weighing 3. Two equal piles with one coin left out.

If they balance then the false coin is the one you left out.

Weighing 4. You now have only 3 coins to deal with. Put one on each scale-pan and leave one out. If they balance then the false coin is the one you left out.

If you were lucky you could do it in one weigjhing, the coin that you left out being the false coin. But , according to the Universal Law of Aggravation, most times you will have to do 4.