ARITHMETIC.
Arithmetic is the study of numbers and their uses. Numbers are expressed by figures.
These figures are:
| 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 9 | 0 |
| One, | Two, | Three, | Four, | Five, | Six, | Seven, | Eight, | Nine, | Zero. |
The figure zero is never read. It merely indicates that that order is omitted.
Numbers greater than 9 are expressed by writing two or more figures side by side.
| Trillions. | Hundred billions. | Ten billions. | Billions. | Hundred millions. | Ten millions. | Millions. | Hundred thousands. | Ten thousands. | Thousands. | Hundreds. | Tens. | Units. | Decimal point. | Tenths. | Hundredths. | Thousandths. | Ten thousandths. | Hundred thousandths. | Millionths. | ||||||
| 4, | 3 | 2 | 4, | 2 | 0 | 8, | 0 | 4 | 2, | 2 | 8 | 9 | . | 0 | 0 | 2 | 4 | 8 | 2 |
Our system of numbers is based on the decimal system.
Every time we move a figure one place to the left of the decimal point, we multiply it by 10.
Every time we move a figure one place to the right of the decimal point, we divide it by 10.
Every three figures in any number, counting from the decimal point to the left, form a period.
Periods of figures are separated from each other by commas.
The names of the periods in order from the decimal point to the left are,
| Trillions | Billions | Millions | Thousands | Units | |||||||||||||||
| Hundred trillions. | Ten trillions. | Trillions. | Hundred billions. | Ten billions. | Billions. | Hundred millions. | Ten millions. | Millions. | Hundred thousands. | Ten thousands. | Thousands. | Hundreds. | Tens. | Units. | |||||
We very seldom use numbers above millions.
