- Choose a 2-digit number ending in 7.
- The last digit of the answer is always 9: _ _ _ 9
- Multiply the first digit by 4 and add 4

(keep the carry): _ _ X _ - Multiply the first digit by the next consecutive number and

add the carry: the product is the first two digits:

XX _ _.

#### Example:

- If the number is
**47**: - The last digit of the answer is 9: _ _ _ 9
- Multiply the first digit (4) by 4 and add 4

(keep the carry): 4 × 4 = 16, 16 + 4 = 20; the next

digit of the answer is 0 (keep carry 2): _ _ 0 9 - Multiply the first digit (4) by the next number (5)

and add the carry (2):

4 × 5 = 20, 20 + 2 = 22 (the first two digits): 2 2 _ _ - So
**47 × 47 = 2209**.

** See the pattern?**

- For 67 × 67
- The last digit of the answer is 9: _ _ _ 9
- Multiply the first digit (6) by 4 and add 4 (keep the

carry): 4 × 6 = 24, 24 + 4 = 28; the next digit of the

answer is 0 (keep carry 2): _ _ 8 9 - Multiply the first digit (6) by the next number (7)

and add the carry (2):

6 × 7 = 42, 42 + 2 = 44 (the first two digits): 4 4 _ _ - So
**67 × 67 = 4489**.

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