16 Jul

### Counting on one hand and on two

A human hand carries five fingers; two hands have ten of them. Undoubtedly, this fact is responsible for the universal adoption of the decimal system.

Children learn to count by counting fingers, first to 5 on one hand and then to 10 on two hands. However, there is a simple way to count to 10 with just 5 fingers of one hand and to 100 using both hands.

This is how:

one | two | three | four | five |
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six | seven | eight | nine |
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A folded fist may stand for 10 if you do not plan to use the second hand, or for 0 if you do:

ten/zero |
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The second hand is used in the same manner but for counting 10s:

ten | eleven |
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twenty six | fifty five |
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(There is an interesting discussion on the web concerning finger counting.)

Thank you for this explanation! It finally made me understand how Soroban works. Here is where I explain it, using your photos: http://www.moebiusnoodles.com/2014/07/abacus-finger-math/

July 29th, 2014 at 6:26 am