Multiplying a multi-digit sequence of numbers
                   by 8 and adding the last digit

1. Choose a number made up of consecutive digits beginning with 1 (123, 1234 etc.).
2. Multiply it by 8 and add the last digit of the original number.
3. The answer will have the same number of digits as the first number selected; the digits will be decreasing digits starting with 9.

   Example:

1. If the number selected is 12345:
2. Multiply by 8, add 5:
3. The answer is 98765 (5 digits).
4. So 12345 multiplied by 8 plus 5 is 98765.

   See the pattern?

1. If the number selected is 12345678:
2. Multiply by 8, add 8:
3. The answer is 98765432 (8 digits).
4. So 12345678 multiplied by 8 plus 8 is 98765432.

More than one example will probably give away the secret, but this ought to be good for one-shot tries.