## 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 101

1. Select a 2-digit number .
2. Write it twice!

#### Examples:

1. 47 × 101 = 4747.
2. 38 × 101 = 3838.
3. 96 × 101 = 9696.

### Multiplying a 3-digit number by 101

1. Select a 3-digit number .
2. The sum of the first and third digits will be the middle digit: _ _ X _ _.
3. The first two digits plus the carry will be the first digits: X X _ _ _.
4. The last two digits of the number will be the last digits: _ _ _ X X.

#### Example:

1. The number chosen is 318.
2. 3 + 8 = 11 (sum of first and third digits):
_ _ 1 _ _ (keep carry, 1)
3. 31 + 1 = 32 (first two digits plus carry):
3 2 _ _ _.
4. The last two digits are the same:
_ _ _ 1 8.
5. So 318 × 101 = 32118.

See the pattern?

1. If the number chosen is 728:
2. 7 + 8 = 15 (sum of first and third digits):
_ _ 5 _ _ (keep carry, 1)
3. 72 + 1 = 73 (first two digits plus carry):
7 3 _ _ _.
4. The last two digits are the same:
_ _ _ 2 8.
5. So 728 × 101 = 73528.