## BEATCALC:  Beat the Calculator!

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 From B. Lee Clay

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### Multiplying a 2-digit number by 9 5/7

1. Multiply the number by 7.
2. Add a zero.
3. Subtract the original number twice.
4. Divide by 7.

#### Example:

1. If the 2-digit number chosen to multiply by 9 5/7 is 21:
2. Multiply by 7: 7 × 21 = 147
3. Add a zero: 1470
4. Subtract the original number twice: 1470 - 21 - 21 =
1470 - 40 - 2 = 1430 - 2 = 1428
5. Divide by 7: 1428/7 = 204
6. So 21 × 9 5/7 = 204.

See the pattern?

1. If the 2-digit number chosen to multiply by 9 5/7 is 71:
2. Multiply by 7: 7 × 71 = 497
3. Add a zero: 4970
4. Subtract the original number twice: 4970 - 71 - 71 =
4970 - 140 - 2 = 4830 - 2 = 4828
5. Divide by 7: 4828/7 = 689 5/7
6. So 71 × 9 5/7 = 689 5/7.

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