## 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 repeating 5's number by 25

1. Choose a repeating 5's number (5555, etc.)
2. Multiply it by 25
3. The product is:
- the first two digits are 13
- the next digits are repeating 8's -- two fewer than repeating 5's in the original number
- the last two digits are 75

#### Example:

1. If the first number is 55555:
- the first two digits are 13: 13.
- the next digits are repeating 8's -- two fewer than repeating 5's in the original number: 888.
- the last two digits are 75: 75.
2. So 25 × 55555 = 1388875.

See the pattern?

1. Next pick is 55555555:
- the first two digits are 13: 13.
- the next digits are repeating 8's -- two fewer than repeating 5's in the original number: 888888.
- the last two digits are 75: 75.
2. So 25 × 55555555 = 1388888875.