The 11x Magic Shortcut

Ever wish you could multiply by 11 super fast in your head? Get ready to amaze your friends with this simple trick!

Subject: mental-calculation • Classes: 6–12 • Difficulty: basic

The Trick

To multiply any two-digit number by 11: 1. Take the two digits of the number. 2. Add them together. 3. Place their sum in between the original two digits. That's it! If the sum is a two-digit number (e.g., 10 or more), carry over the 'tens' digit to the left.\n\nWHY it works: Think of $N \times 11$ as $N \times (10 + 1) = N \times 10 + N \times 1$. For a number $AB$, it's $(10A+B) \times 11 = 110A + 11B = 100A + 10A + 10B + B = 100A + 10(A+B) + B$. This structure directly creates the 'sum in the middle' pattern.

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