Back to Calculation Tips & Tricks

Squaring Numbers

Multiplying Numbers

Dividing Numbers

Adding Numbers

Subtracting Numbers

Finding Percents

Calculation Practice Exercises

Full List

One fewer 9 than the repeating 9's: 9 9 82 8 2 same number of 0's as 9's in the square 0 0 a final 81 8 1

So 9991 × 9991 = 99820081.

See the pattern?

one fewer 9 than the repeating 9's: 9 9 9 9 82 8 2 same number of 0's as 9's in the square 0 0 0 0 a final 81 8 1

Those big products ought to impress your friends, and they will need a BIG calculator to keep up with you!

[Privacy Policy] [Terms of Use]

Home || The Math Library || Quick Reference || Search || Help