Add a sequence from one to a selected
             1-digit number and back

1. Choose a 1-digit number.
2. Square it.

   Example:

1. If the 1-digit number selected is 7:
2. To add 1 + 2 + 3 + 4 + 5 + 6 + 7 + 6 + 5 + 4 + 3 + 2 + 1
3. Square 7: 49
4. So the sum of all numbers from 1 through 7 and back is 49.

   See the pattern?

1. If the 1-digit number selected is 9:
2. To add 1 + 2 + 3 + 4 + 5 + 6 + 7 + 8 + 9 + 8 + 7 + 6 + 5 + 4 + 3 + 2 + 1
3. Square 9: 81
4. So the sum of all numbers from 1 through 9 and back is 81.

You will certainly be faster with your answer than someone adding all the numbers up on a calculator!