Calculator Puzzle: Four-Digit Numbers Always Divisible by 11?
2025-01-03
A blog post presents a mathematical puzzle involving a standard calculator keypad. The puzzle challenges players to press four digit keys forming the corners of a square or rectangle, creating a four-digit number. The post elegantly proves that regardless of the chosen square or rectangle, the resulting four-digit number will always be divisible by 11. Multiple proof methods, including algebraic and pattern-based approaches, are explored, sparking an engaging discussion on mathematical patterns.