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

See the pattern?

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

Posted in: Mathematics Tips,Squaring Numbers