The 11x Magic Multiplier!

Ever wished you could multiply by 11 super fast, without a calculator? Unleash your inner math wizard and impress everyone!

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

The Trick

To multiply any two-digit number by 11, simply 'sandwich' the sum of its digits between the original digits! \n\n1. Take the two-digit number, say $ab$. \n2. Add the digits: $a+b$. \n3. Place the sum $(a+b)$ in between $a$ and $b$. If $a+b$ is a two-digit number (e.g., 10 or more), write down the units digit of the sum and carry over the tens digit to $a$. \n\n**Why it works:** When you multiply $ab$ by $11$, it's like multiplying $(10a+b)$ by $(10+1)$. This gives $100a + 10b + 10a + b = 100a + 10(a+b) + b$. This perfectly aligns with $a$ (hundreds place), $(a+b)$ (tens place), and $b$ (units place)!

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