π is an irrational number, which means it CANNOT be written as a terminating decimal (like 3.14) or a fraction (like 22/7). Both 3.14 and 22/7 are only approximations.
π is defined as the ration of the circumference of a circle to its radius. Click this link for a cool video someone else made showing why π is close to 22/7.
Alternative Arithmetic Methods (I think these are easier ways to add, multiply, etc.)
Scratch Addition (scratchadd.mp4): Show a quick and easy way to add a column of single digit numbers using the Scratch or Dot Method. http://youtu.be/aobn006_rl0
Multiply by 9 the easy wayThis video shows you easy ways to multiply single digits by 9, and larger numbers when all the digits are the same, like 88888 x 9...really easy and fun to do!
Shows the original numerals and the code for how it was obvious what each numeral stood for. These are referred to as the Arabic numerals, the Hindu numerals, Hindu-Arabic numerals and/or the Indian numerals. I do not know the exact origins.
Squaring numbers whose digits are all ones; fun pattern for multiplying numbers by themselves (squaring) if all its digits are 1....like 11 x 11 or 11111 x 11111, etc. Show your friends!
Square Numbers that end in 5 such as 85 time 85, etc.: http://www.youtube.com/watch?v=Jeh83AoJ0v4
Videos by others:
This is old footage (not by me) and very funny:
Calculus: This is the Derivate Rag (a song about how to remember how to take derivatives): http://www.youtube.com/watch?v=lQElwkuyiks