- Take a 2-digit number beginning with 1.
- Square the second digit

(keep the carry) _ _ X - Multiply the second digit by 2 and

add the carry (keep the carry) _ X _ - The first digit is one

(plus the carry) X _ _

#### Example:

- If the number is
**16**, square the second digit:

6 × 6 = 36 _ _ 6 - Multiply the second digit by 2 and

add the carry: 2 × 6 + 3 = 15 _ 5 _ - The first digit is one plus the carry:

1 + 1 = 2 2 _ _ - So
**16 × 16 = 256**.

** See the pattern?**

- For 19 × 19, square the second digit:

9 × 9 = 81 _ _ 1 - Multiply the second digit by 2 and

add the carry: 2 × 9 + 8 = 26 _ 6 _ - The first digit is one plus the carry:

1 + 2 = 3 3 _ _ - So
**19 × 19 = 361**.

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