This version of the classic riddle involves 12 coins but popular variations can consist of 12 marbles or balls.

Counterfeit coin riddle.

Both groups weigh the same. A king challenges his wisest counselor to figure out which of the nine coins is a counterfeit. To make it as difficult as possible the counselor can only use the balance twice. If they balance we know coin 12 the only coin not weighed is the counterfeit one. Otherwise the coins look identical. This version of the classic riddle involves 12 coins but popular variations can consist of 12 marbles or balls.

Otherwise the coins look identical. Part of the appeal of this riddle is in the ease with which we can decrease or increase its complexity. Number the coins 1 through 12. If they balance weigh coins 9 and 10 against coins 11 and 8 we know from the first weighing that 8 is a good coin. You re the realm s greatest mathematician but ever since you criticized the emperor s tax laws you ve been locked in the dungeon. The counterfeit one is slightly heavier than the other seven.

You are given eight coins and told that one of them is counterfeit. This means that the counterfeit coin is in the group with 2 coins. The counterfeit coin is heavier than the others. Can you earn your freedom by finding the fake. Split the coins into 3 groups 2 groups with 3 coins each and 1 group with 2 coins. The counterfeit one is slightly heavier than the other seven.

Weigh coins 1 2 3 4 against coins 5 6 7 8. Using a simple balance scale how can you determine which coin is counterfeit using the scale only twice. How does he accomplish this task. The counterfeit coin riddle is derived from the mathematics field of deduction where conclusions are systematically drawn from the results of prior observations. So take the 2 coins from that group and use the scale to determine the counterfeit coin. The counterfeit coin riddle is derived from the mathematics field of deduction where conclusions are systematically drawn from the results of prior observations.

Luckily for you one of the emperor s governors has been convicted of paying his taxes with a counterfeit coin which has made its way into the treasury.