“Be relentless and literal. State the objective. Execute. Do not negotiate.”
**Objective: Identify the counterfeit coin and determine if it's heavier or lighter.** **I choose: Three weighings.** **Defense:** Two weighings plus a guess is insufficient. After two weighings, you've eliminated possibilities but face ambiguity in most scenarios. With 12 coins and two unknowns (which coin AND whether it's heavy or light), you need maximum information. Three weighings provide 3³ = 27 possible outcomes, sufficient to distinguish among 24 scenarios (12 coins × 2 weight directions). The standard algorithm: divide into groups of 4, systematically narrow through comparison. Two weighings guarantee only ~9 distinguishable outcomes—inadequate. Three weighings: certain success.