Consider the following table for approximations of the value of pi, which we use in absence of a scientific calculator:

Approximation	Decimal value	Error (av - pi) / pi
pi	3.14159265359	0%
22 / 7	3.142857142857	0.04%
355 / 113	3.141592920354	0.000000849%

How do you remember this?

• Take the first 3 odd numbers, write them down twice in sequence: 113355
• Now, split this number in the middle: 113  355
• Divide 355 by 113
• Easy, isnt it?