## 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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Calculation
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### Multiplying a repeating 1's number by 12

1. Choose a repeating 1's number (111, etc.)
2. Multiply it by 12
3. The product is:
- first digit is 1
- next digits are 3's - one fewer than repeating 1's in the original number
- last digit is 2.

#### Example:

1. If the first number is 11111:
2. Multiply by 12. The product is:
first digit is 1: 1
next digits are 3's, one fewer than 1's: 3333
last digit is 2: 2
3. So 11111 × 12 = 133332.

See the pattern?

1. If the first number is 11111111:
2. Multiply by 12. The product is:
first digit is 1: 1
next digits are 3's, one fewer than 1's: 3333333
last digit is 2: 2
3. So 11111111 × 12 = 133333332.
With these three steps you will be able to give these big products with ease. Your calculator-using friend will run out of digits with these big numbers.