Multiply by 11 Trick
💡 How to solve ▾
Multiplying by 11 is the same as multiplying by 10 and adding the number once more. For two-digit numbers you can also spread the digits and add the middle.
A worked example
11 × 63: think 63 × 10 = 630, plus 63, gives 693. The digit trick: 6 _ 3 with 6+3=9 in the middle also gives 693.
Questions people ask
What happens when the middle digits add to more than 9? ▾
Carry the extra into the next digit. For 11 × 76, the middle is 7 + 6 = 13, so you write 3 and carry 1 into the 7, giving 836.
Does the trick work for three-digit numbers? ▾
Yes, but the ×10-plus-itself method scales better there. Add each digit to its neighbour from right to left and carry as needed.