## 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 a 2-digit number by 10001               and adding 21

The product of a 2-digit number and 10,001 + 21 is:

1. the two digits,
2. two zeros,
3. the two digits,

#### Example: 29 × 10001 + 21

1. 29 × 10001 = 290029
2. 290029 + 21 = 290050

### Multiplying a 3-digit number by 10001               and adding 201

The product of a 3-digit number and 10,001 + 201 is:

1. the three digits,
2. one zero,
3. the three digits,

#### Example: 436 × 10001 + 201

1. 437 × 10001 = 4370437
2. 4370437 + 201 = 4370638

### Multiplying a 4-digit number by 10001               and adding 2001

The product of a 4-digit number and 10,001 + 2001 is:

1. the four digits, repeated once

#### Example: 6741 × 10001 + 2001

1. 6741 × 10001 = 67416741
2. 67416741 + 2001 = 67418742

Create variations by changing the number to be added or subtracted - just make the number an easy one to handle mentally.