Our counting system is based on the number 10 (10 fingers).
The main principle of the decimal system is that 10 is considered as a new unit from which point counting starts again. Ten tens is again a new unit. The multiples of 10 are counted by the same systems as 1 to 9.
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 10 |
| 11 | 12 | 13 | 14 | 15 | 16 | 17 | 18 | 19 | 20 |
| ' | ' | ' | ' | ' | ' | ' | ' | ' | |
| ' | ' | ' | ' | ' | ' | ' | ' | ' | |
| ' | ' | ' | ' | ' | ' | ' | ' | ' | |
| 91 | 92 | 93 | 94 | 95 | 96 | 97 | 98 | 99 | 100 |
Remember that no decimal number-system spoken words like twenty three belong to the decimal counting system, 23 belongs to the decimal number notation.
Origins of decimal counting system are hidden - we can see the spread or diffusion of our system because people wanted to trade with us.
Other Counting Methods 
The Development of Counting Systems and Notations History of Mathematics Module 
Links to other History of Mathematics sites
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These pages are maintained by M.I.Woodcock.