Multiply by 11
For 2-digit numbers, put the sum of the digits in the middle. 53 × 11 = 583.
How long?
Type the answer. Correct answers move on by themselves. Press Enter to skip a wrong one.
How the trick works
- Split the 2-digit number into its two digits.
- Add the digits together.
- Put that sum between them. If it is 10 or more, carry the 1 to the first digit.
Worked examples
53 × 11: write 5 and 3 with a gap, 5 _ 3.
Put 5 + 3 = 8 in the gap: 583.
27 × 11: write 2 and 7 with a gap, 2 _ 7.
Put 2 + 7 = 9 in the gap: 297.
86 × 11: 8 + 6 = 14, which is 10 or more.
Write 4 in the middle and carry 1 to the 8, which makes it 9: 946.
Practise it
Take the 1 minute drill above a few times. When you can do most of them without slowing down, try level 3, which mixes this trick with others.