## 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 64

1. Select a 2-digit number.
2. Multiply it by 11.
3. Multiply this product by 6.
4. From this, subtract twice the original number.

#### Example:

1. The 2-digit number chosen to multiply by 64 is 21.
2. Multiply it by 11: 11 × 21 = 231.
3. Multiply this product by 6: 6 × 231 = 1200 + 186 = 1386.
4. From this, subtract twice the original number: 1386 - 2(21) = 1386 - 42 = 1346 - 2 = 1344.
5. So 64 × 21 = 1344.

See the pattern?

1. The 2-digit number chosen to multiply by 64 is 52.
2. Multiply it by 11: 11 × 52 = 572.
3. Multiply this product by 6: 6 × 572 = 3000 + 420 + 12 = 3420 + 12 = 3432.
4. From this, subtract twice the original number: 3432 - 2(52) = 3432 - 104 = 3332 - 4 = 3328.
5. So 64 × 52 = 3328.

Practice multiplying by 11. Remember to multiply and add from left to right.