## BEATCALC:  Beat the Calculator!

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 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

Finding Percents

Calculation
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### Multiplying a 2-digit number by 65

1. Select a 2-digit number.
2. Multiply it by 11 (add digits right to left).
3. Multiply by 6.
4. Subtract the original number.

#### Example:

1. The 2-digit number chosen to multiply by 65 is 21.
2. Multiply by 11: right digit is 1, 1+2 = 3,
left digit is 2: 231
3. Multiply by 6: 6 × 231 = 1200 + 186 = 1386
4. Subtract the original number: 1386 - 21 = 1365
5. So 65 × 21 = 1365.

See the pattern?

1. The 2-digit number chosen to multiply by 65 is 52.
2. Multiply by 11: right digit is 2, 2+5 = 7,
left digit is 5: 572
3. Multiply by 6: 6 × 572 = 3000 + 420 + 12 = 3432
4. Subtract the original number: 3432 - 52 = 3380
5. So 65 × 52 = 3380.

Practice multiplying by 11 (sum digits right to left) and subtracting left to right and you will be able to give these products easily and accurately.

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3 February 2003
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