## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

Finding Percents

Calculation
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### Multiplying a repeating 1's number by 17

1. Choose a repeating 1's number (111, etc.)
2. Multiply it by 17
3. The product is:
- first digit is 1
- next digits are 8's - one fewer than repeating 1's in the original number
- last digit is 7.

#### Example:

1. If the first number is 111111:
2. Multiply by 17. The product is:
first digit is 1: 1
next digits are 8's, one fewer than 1's: 88888
last digit is 7: 7
3. So 111111 × 17 = 1888887.

See the pattern?

1. If the first number is 1111111111:
2. Multiply by 17. The product is:
first digit is 1: 1
next digits are 8's, one fewer than 1's: 888888888
last digit is 7: 7
3. So 1111111111 × 17 = 18888888887.
Follow these three steps and you will be able to give these big products quickly and accurately. How will your friend using a calculator handle these?