## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

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### Multiplying a repeating 9's number by 77

1. Choose a repeating 9's number (e.g., 9999).
2. The product is made up of:
- first two digits are 76.
- next digits are repeating 9's -- two fewer than repeating 9's in original number.
- last two digits are 23.

#### Example:

1. The repeating 9's number chosen to multiply by 77 is 999.
2. First two digits are 76.
3. Next digits are repeating 9's -- two fewer than repeating 9's in original number: 9.
4. Last two digits are 23.
5. So 77 × 999 is 76923.

See the pattern?

1. The repeating 9's number chosen to multiply by 77 is 99999.
2. First two digits are 76.
3. Next digits are repeating 9's -- two fewer than repeating 9's in original number: 999.
4. Last two digits are 23.
5. So 77 × 99999 is 7699923.
Follow these three steps and you will be giving these large products quickly.