## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Subtracting Numbers

Finding Percents

Calculation
Practice Exercises

Full List

### Multiplying two 2-digit numbers(difference of 1)

1. Choose a 2-digit number.
2. Select a number either 1 smaller or 1 larger.
3. Square the larger number (multiply it by itself).
4. Subtract the larger number from the product.
OR
5. Square the smaller number (multiply it by itself).
6. Add the smaller number to the product. Pick the easier one to square.

#### Example:

1. If the first number is 76, choose 75 as the second number.
2. 75 × 75 = 5625 (square the smaller). Remember how to square a two-digit number ending in 5?
3. 5625 + 75 = 5700 (add the smaller).
4. So 76 × 75 = 5700.

See the pattern?

1. If the first number is 32, choose 31 as the second number.
2. 32 × 32 = 1024 (square the larger). Remember how to square a two-digit number ending in 2?
3. 1024 - 32 = 992 (subtract the larger).
4. So 32 × 31 = 992.