Multiply by 11 in a Flash!

Ever wished you could multiply any number by 11 instantly, without a calculator? No problem! This trick makes you a math magician!

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

The Trick

The 'Sandwich' method for multiplying by 11! For any two-digit number $AB$ (where $A$ is the tens digit and $B$ is the units digit): 1. Write down the unit digit $B$ at the end. 2. Add the two digits together: $A+B$. 3. Write down the tens digit $A$ at the beginning. 4. Combine them: $A(A+B)B$. If $A+B$ is a two-digit number, carry over the tens digit to $A$. WHY it works: $N \times 11 = N \times (10+1) = (N \times 10) + N$. For $10A+B$, this is $100A + 10B + 10A + B = 100A + 10(A+B) + B$.

Study More with GyanAI

GyanAI is a free AI tutor for CBSE students. Ask any question for an instant step-by-step answer. Try GyanAI free.