Squaring a 2-digit number beginning with 1

1. Take a 2-digit number beginning with 1.
2. Square the second digit
   (keep the carry)   _ _ X
3. Multiply the second digit by 2 and
   add the carry (keep the carry)   _ X _
4. The first digit is one
   (plus the carry)   X _ _

   Example:

1. If the number is 16, square the second digit:
   6 x 6 = 36   _ _ 6
2. Multiply the second digit by 2 and
   add the carry: 2 x 6 + 3 = 15   _ 5 _
3. The first digit is one plus the carry:
   1 + 1 = 2   2 _ _
4. So 16 x 16 = 256.

   See the pattern?

1. For 19 x 19, square the second digit:
   9 x 9 = 81   _ _ 1
2. Multiply the second digit by 2 and
   add the carry: 2 x 9 + 8 = 26   _ 6 _
3. The first digit is one plus the carry:
   1 + 2 = 3   3 _ _
4. So 19 x 19 = 361.