Beat the Calculator

Take a look at ”Beat the Calculator”. I think Ralphie especially will like this site.

http://mathforum.org/k12/mathtips/beatcalc.html

I found this through the math class I'm taking.
This webpage includes hundreds of mental calculation tricks for adding, subtracting, multiplying, dividing, squaring numbers and finding percentages. Pick a few tricks and practice them until you can do the calculation quickly. Then find a colleague, friend, or family member to test your skill. Can you use the calculation trick to get an answer more quickly than the person using a calculator?