## BEATCALC:  Beat the Calculator!

Back to Calculation Tips & Tricks

 From B. Lee Clay

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Adding Numbers

Subtracting Numbers

Finding Percents

Calculation
Practice Exercises

Full List

### Multiplying a 2-digit number by 7 3/4

1. Select a 2-digit number.
2. Multiply by 3.
3. Add one zero.
4. Add the original number.
5. Divide by 4.

#### Example:

1. The 2-digit number chosen to multiply by 7 3/4 is 21.
2. Multiply by 3: 3 × 21 = 63
3. Add one zero: 630
4. Add the original number: 630 + 21 = 651
5. Divide by 4: 651/4 = 162 1/4
6. So 21 × 7 3/4 = 162 1/4.

See the pattern?

1. The 2-digit number chosen to multiply by 7 3/4 is 71.
2. Multiply by 3: 3 × 71 = 213
3. Add one zero: 2130
4. Add the original number: 2130 + 71 = 2201
5. Divide by 4: 2201/4 = 550 1/4
6. So 71 × 7 3/4 = 550 1/4.

[Privacy Policy] [Terms of Use]

© 1994- The Math Forum at NCTM. All rights reserved.
http://mathforum.org/

Web page design by Sarah Seastone