You are given 12 coins that are identical except that they are numbered and you are told that one coin is odd-weighted, being either slightly lighter or slightly heavier than any one of the remaining eleven. You are given a worktable and a balance beam scale. You may use the scale three times only. You must tell at the end of three weighings; which coin is odd-weighted and whether it is heavy or light. Outline your solution in less than one thousand words.