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27 Coins

There are 27 coins. All coins has same weight except one is heavier. All coins looks identical.

What is the minimum number of weighing required to certainly find the heavier coin?

The point of this question is find an answer that will work everytime. The answer will not reply on accidentally guessing the right coin.

Hints

When ansering these types of questions, sometimes there are hints in the numbers. Ask youself, why did the question use this number?

Solution

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**Solution: 3** In each step you will weigh one third of the coins against one third of the coins while one third remains off the scale. If the left is heavier keep the left coins, if the right is heavier keep the right coins, if they are equal keep the coins not on the scale. 1) Put 9 each on each side of balance and eliminate two sets; remaining 9 2) Put 3 each on each side of balance and eliminate the two sets; remaining 3 3) Put 1 each on each side of balance and eliminate the two; remaining 1

Notes

Many of these types of questions require you to look for information in silence. For example, with this question, you can weigh nine coins against nine coins and still learn something about the nine coins not on the scale.

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