stone tablets strewn with sand, which were marked off columns for recording numbers. For hundreds of year computations had to be carried out upon an abacus stone tablet. In trading with the Hindus, the Arabs learned simple new numerals and their use. The Arabs also tr with the peoples of southern Europe, to whom they bro the new numerals. In this way the Hindu numerals spread over the entire civilized world. Because the A brought them into Europe, the numerals have been i rectly called Arabic. We use the nine numerals to form numbers in much same way as we use letters to form words. The nine merals and the zero are thus a sort of number alphabet. same numerals are used in the different countries, whi not the case with the letters. The printed and writter merals are very nearly alike, while the printed and w letters differ very much. About two hundred fifty years ago the words mi billion, trillion, quadrillion, and so on, came into u northern Europe. In the United States large number separated into periods of three, as is here shown: tem I, V, X, L, C, D, M stand for 1, 5, 10, 50, 1,000. A dash placed above a symbol multiplies it Thus, V = 5,000. = 5,000. A symbol placed before a larg subtracted from it. Thus 4 is made by IV, exc clocks have IIII; 9 by IX; 40 by XL; 90 by XO CD; 900 by CM. In all other cases a symbol after an equal or larger one and added to it. Thus, 56 is LVI; 65 is LXV; 70 is LXX. The Roman number system was invented by th ancient Rome long before the Hindu system, of have just read. The Roman number system was number system until 1200 A. D. Now it is used on different forms of numerals are needed. Where seen the Roman numerals? Can you make boys' and girls' names out of the fo 4. Reading and Writing Numbers.-Large numbers ally arise only in connection with national affairs, as sta a country's area in square miles, a nation's debts, and so Ordinary numbers contain six digits or less and are differently by business and scientific men from what have been used to in reading numbers. For instance, 456 is read "forty-five, sixty-two, ninety-one"; 73024 is "seven, thirty, twenty-four." Notice that "and" is n used; that comes only in decimals, which we shall study la Telephone numbers are called to the operator in y different way. Each digit is named separately so that 3 is called "three, six, four, eight." It is often necessary to write out numbers in words on bank checks. For instance, 356 is written three hund fifty-six, while 3064 is written three thousand sixty-f Again notice that and has not been used. Such num as fifty-six and forty-one are compound words and mus written with the hyphen. Read the first six numbers above as telephone numbe Write the first six numbers above in words. dition require that the forty-five addition combina 4 +7, be memorized thoroughly. You must kı 4+7 and 7 + 4 equal 11 as quickly as you do tha cat. Do not memorize the combinations as table 3's, etc., but learn each combination alone as a fact. That is the only way you use the combinati EXERCISES Give the sum of each digit in the following with just below it. Give the sum of each digit with the to its right. Find the sum of each column; add both and downward to check your result. 6. Adding 9's and 8's.—In adding 9 to a two-dig ber note that the ten's digit is merely increased 1, w unit's digit is decreased 1. In adding 8 the ten's increased 1 while the unit's digit is decreased 2. Without the use of pencil and paper give as rapidly as] sible the sums of the following: 60 28 36 46 43 67 4 8 95 4 8 64 9 78 58 29 7 9 89 74 8 9 8 69 7. Addition of Columns of Numbers.-First find the sum of the units' column to be 24, or 4 units and 2 tens. The 4 is written under units' ten above the tens' column. 31, or 1 ten and 3 hundreds. tens' column, and the 3 above the hundreds' column. Further additions are carried on in the same manner. |