6. Summary: (1) There are ten separate symbols used in our system (the Hindu-Arabic system) of writing numbers. These symbols are called figures, numerals, or digits. (2) Each figure has a figure value and a place value. Thus, the figure value of zero is naught; but a zero that occupies a place in a number may be very important. (3) The place each figure occupies in a number is called an order. (4) In large numbers the figures are grouped by threes; these groups of threes are called periods. (5) The names of the orders (single places) in each period are limited to three. Beginning at the right they are: Units (or ones), tens, and hundreds. (See the preceding table.) ཎྞ (6) The names of the periods are units (or ones), thousands, millions, billions, trillions, etc. (See the table, p. 3.) A million is a thousand thousand. A billion is a thousand million. A trillion is a thousand billion. (7) The relation between successive orders is one of tens; that is, the number value of a figure is multiplied by ten when it is moved from one order to the next order to its left, and divided by ten when it is moved to the next order to its right. (8) The two essential things are: (a) To be able to read and write any number of three figures. (b) To know the names of the periods. Practice in these essentials is afforded by the exercises that follow. EXERCISES A. Write in figures each of the following numbers: 1. Two thousand, twenty-six. 2. Five thousand, two hundred one. 3. Thirty thousand, three hundred three. 4. Fifty-six thousand, nine. 5. Three hundred thousand, seventy-eight. 6. Nine hundred twenty-five thousand, nine. 7. Seventy thousand, seven. 8. Sixty thousand, sixty-three. 9. One million, two thousand, three. 10. Three million, four hundred three thousand, three hundred four. B. Write in words each of the following numbers: C. Express in words and also in figures each of the following numbers: 1. The population of your state. 2. The population of the United States. 3. The number of feet in one mile; also the number of inches in one mile. 4. The area of your state. 5. The area of New England; the Middle States; the South Atlantic States; the North Central States; the South Central States; the Western States. II. THE READING AND WRITING OF DECIMALS 7. A decimal fraction, or a decimal, is a fraction whose denominator is 10, 100, or 1000, etc. The denominator is not written, but is expressed by the decimal point (.) placed in front of the numerator. 8. To express some decimals one or more zeros have to be inserted between the decimal point and the numerator. 9. An integer and a decimal together, called a mixed decimal, express a mixed number. 10. To read a decimal, read it as a whole number and then give it the name of the last decimal place. Thus: .206 is read two hundred six thousandths. .0322 is read three hundred twenty-two ten-thousandths. To read a mixed decimal, read the integral part (the whole number) as usual, use and at the decimal point, and then read the decimal. Thus : 7.206 is read seven and two hundred six thousandths. 212.2581 is read two hundred twelve and two thousand five hundred eighty-one ten-thousandths. 11. The table below shows the arrangement of orders in our decimal system. Beginning at the decimal point, name the decimal orders. Read each number given in the table. EXERCISES Read each of the following numbers: 1. .2, .02, .023, .020, .0026 2. 3.2, 14.02, 5.026, 5.202, 6.305 3. 256.203, 102.2603, 200.031, 2002.02 4. 3010.010, 5002.002, 30.030, 43.043 |