you first sort them into groups of the
same kind - 25 Satang, 50 Satang, 1 Baht, 5 Baht, 10 Baht, and
then group them by tens. The number ten is due to the number of
your fingers; you know how to use them for simple calculations! When you play cards, dice or
domino, you see natural number
symbols which are useless for large
numbers. It is confusing to represent the number 878 by 878
slashes (/), dots (.) or whatever. Hence people began to group numbers, just as
you do when you count the coins in your money box; you first sort them into groups of the
same kind - 25 Satang, 50 Satang, 1 Baht, 5 Baht, 10 Baht, and
then group them by tens. The number ten is due to the number of
your fingers; you know how to use them for simple calculations!
Other groups are 12 in the dozen, 144 in the gross (12 dozen), 60 seconds in the minute, 60 minutes in the hour, 24 hours in the day, 360 degrees in the circle. These first occurred at Babylon many years ago when people made astronomical observations and land surveys.
The dozen (12) has the 4 factors 2, 3, 4, 6, the minute (60) the 10 factors 2, 3, 4, 5, 6, 10, 12, 15, 20, 30, while 10 has only the two factors 2, 5. Mental calculations with groups 12 and 60 were much easier than with 10 until decimals were invented!
With groups came number symbols in Egypt, Babylon and elsewhere:
Still 1000 years ago, Europeans used the seven Roman numerals
| I | V | X | L | C | D | M |
| 1 | 5 | 10 | 50 | 100 | 500 | 1000 |
They employed addition:
Rule 1. Placement of equal symbols side by side:
| II | III | XX | XXX | CC | CCC | etc. |
| 2 | 3 | 20 | 30 | 200 | 300 |
Rule 2. Placement of smaller values after larger ones:
| VI | XI | XXI | XXXI | LX | CX | DC |
| 6 | 11 | 21 | 31 | 60 | 110 | 600 |
| VII | XII | XXII | XXXII | LXX | CXX | DCC |
| 7 | 12 | 22 | 32 | 70 | 120 | 700 |
| VIII | XIII | XXIII | XXXIII | LXXX | CXXX | DCCC |
| 8 | 13 | 23 | 33 | 80 | 130 | 800 |
| MC | MCC | MCCC | MD | |||
| 1100 | 1200 | 1300 | 1500 |
amd subtraction:
Rule 3. Placement of smaller values ahead of larger ones:
| IV | IX | XL | XC | CD | CM |
| 4 | 9 | 40 | 90 | 400 | 900 |
Indian symbols had different rules. They became our
nine 
numbers 1, 2, 3, 4, 5, 6, 7, 8, 9. Their significance was due to their position in sets of numbers. Units were placed at the right end of a composite number
(385), followed on the left by tens, hundreds, etc. - the position value system. Lack of a value, for example of hundreds and units in
3040, was indicated by a dash (3
/ 4 / = 3040). Finally (~ 400 A.C.), "nothing" became a number (zero); it was first denoted by a dot (·) or a circle
(o) and only later
by 0. This completed the position system.
Indians used mainly mental arithmetic.
The Arabs adopted the Indian number system and brought it to North Africa and Spain in the 12th Century. Gradually, the Europeans replaced Roman numbers by Arabic numbers.
The modern, electronic computer - a system of switches which can be turned on or off - uses binaries.
When you read a number in the position system, 385 becomes "three hundred eighty five".
They simplify computations. Initially words were used instead of symbols. The fraction symbol (/) came from the Arabs, the plus (+) and minus (-) symbol from the Germans, the equality symbol (=) from the French and the multiplication symbol (×) from the English. The Germans replaced × by a point (·) and the fraction sign (/) by a colon (:).
You now know very well all these rules, which were developed step by step.