## 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 2-digit number by 9.3

1. Multiply the number by 3.
2. Move decimal point one place left.
3. Add this to nine times the original number.

#### Example:

1. The 2-digit number chosen to multiply by 9.3 is 21.
2. Multiply by 3: 3 × 21 = 63.
3. Move decimal one place left: 6.3.
4. Add this to nine times the original number: 6.3 + 9(21) = 6.3 + 189 = 195 + .3 = 195.3.
5. So 9.3 × 21 is 195.3.

See the pattern?

1. The 2-digit number chosen to multiply by 9.3 is 61.
2. Multiply by 3: 3 × 61 = 183.
3. Move decimal one place left: 18.3.
4. Add this to 9 times original number: 18.3 + 9(61) = 18.3 + 549 = 559 + 8.3 = 567 + .3 = 567.3.
5. So 9.3 × 61 is 567.3.
Remember to add left to right in small, easy-to-handle increments, and this procedure will be an easy one.