Adding even numbers from two through
              a selected 2-digit even number

1. Divide the even number by 2 (or multiply by 1/2).
2. Multiply this result by the next number.

   Example:

1. If the 2-digit even number selected is 24:
2. Divide 24 by 2 (24/2 = 12) or multiply by 1/2 (1/2 x 24 = 12).
3. The next number is 13; 12 x 13 = 156.
   Ways to multiply 13 by 12:
   • Square 12, then add 12: 12 x 12 = 144, 144 + 12 = 156.
   • Multiply left to right. 12 x 13 can be done in steps: 12 x (10+3) = (12 x 10) + (12 x 3) = 120 + 36 = 156.
4. So the sum of all the even numbers from two through 24 is 156.

   See the pattern?

1. If the 2-digit even number selected is 42:
2. Divide 42 by 2 (42/2 = 21) or multiply by 1/2 (1/2 x 42 = 21).
3. The next number is 22; 21 x 22 = 462.
   Ways to multiply 22 by 21:
   • Square 21, then add 21: 21 x 21 = 441, 441 + 21 = 462.
   • Multiply left to right. 21 x 22 can be done in steps: 21 x 22 = (21 x 20) + (21 x 2) = 420 + 42 = 462.
4. So the sum of all the even numbers from two through 42 is 462.