The central limit theorem is pretty cool and is outlined here.

So

toss a coin 100 times

count 1 for each head and 0 for each tail

add these numbers up ->**sum**

now repeat all of the above say 200 times

the 200 **sum** values will be distributed normally

eg

**Sum**/ Number of occurrences

2 /…3

10 /…..5

15 /……..8

23 /…………12

32 /……………………23

41 /……………………………..35

52 /…………………………………………….50

65 /………………………..29

73 /……………15

75 /……….10

82 /….4

93 /….4

95 /.1

100 /.1