Multiplying two digit number by 22

1. Select a 2-digit number.
2. Multiply it by 2.
3. The last digit will be the same. _ _ _ X
4. Add the digits right to left.

Example:

1. The 2-digit number chosen to multiply by 22 is 78.
2. 78 × 2 = 156 (multiply by 2).
3. Last digit is 6. _ _ _ 6
4. Add digits right to left. 6 + 5 = 11 _ _ 1 _
   5 + 1 + 1 (carry) = 7 _ 7 _ _
5. The first digit is the same. 1 _ _ _
6. So 22 × 78 = 1716.