## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

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### Multiplying a repeating 2's number by 99

1. Choose a repeating 2's number (222, etc.)
2. Multiply it by 99
3. The product is:
- the first two digits are 21
- the next digits are repeating 9's (two fewer than repeating 2's in the original number)
- the final two digits are 78

#### Example:

1. If the first number is 22222:
2. First two digits are 21.
3. Next digits are repeating 9's -- two fewer than repeating 2's in the original number: 999.
4. Last two digits are 78.
5. So 99 × 22222 = 2199978.

See the pattern?

1. Next pick is 2222222222:
2. First two digits are 21.
3. Next digits are repeating 9's -- two fewer than repeating 2's in the original number: 99999999.
4. Last two digits are 78.
5. So 99 × 2222222222 = 219999999978.

Follow these three steps and you will be able to give these products quickly and correctly.