One solution is to label the coins with the letters FAKE MIND CLOT and weigh the coins in the following three combinations:
(先把硬幣標上FAKE MIND CLOT"英文字母"的記號, 然後開如下圖方法秤3次)
MA DO -- LIKE
ME TO -- FIND
FAKE -- COIN
全句就是: MA DO LIKE ME TO FIND FAKE COIN.
Logic will now allow you to find the fake coin based on the three results. For instance, if the results were left down, balanced, left down, we could work out which coin is fake in the following way: (假如秤三次的結果分別為: 左低, 平衡, 左低)
A - appears on the left twice and could be fake. 在左邊出現2次, 有機會假
C - appears only once, therefore can't be fake (otherwise the first weighing would be balanced). 只出現一次, 不可能假
K - appears on opposite sides, so it can't make the left side go down both times. 左右兩邊各出現一次, 不可能假
L - appears only once, therefore can't be fake (otherwise the third weighing would be balanced). 只出現一次, 不可能假
Therefore the only possibility is A, which must be heavier. Any other combination of ups and downs will allow you to use the same logic to find the fake coin. (所以A是假的)
