PRACTICAL ARITHMETIC CHAPTER I I. REVIEW OF PRIMARY ARITHMETIC: INTRODUCTION 1. To the pupil. You have already learned much about Arithmetic. You have learned to count and to write numbers, at least to a million, to add, subtract, multiply, and divide integers, and to do some work with fractions and mixed numbers. You have also learned how to write United States money and decimal fractions, how to measure things, and the ordinary tables of denominate numbers. Besides all this, you have seen that you have need for Arithmetic at the store, in your games, in reading, and in many other ways. There is, however, much more to learn about the uses of Arithmetic, and some more to learn about how to work with numbers. Every one of us is interested in what the world is doing, and in our country and its products. We all like to know about our farms, our mines, our forests, our great industries, and the accounts that we must sometime keep, and we find much of interest about these matters in Arithmetic. 1 NOTATION AND NUMERATION ORAL EXERCISE 1.. What name do you give to 3 tens? to 10 tens? 2. What name do you give to 1000 thousands? 3. Looking at your fingers, do you see why people came to count as they do, by tens? Why was it? 4. Read aloud these numbers: 3,505,246 8,421,205 6,006,006 17,243,321 82,603,627 2. Notation. The writing of numbers by means of symbols is called notation. 3. Numeration. The naming of numbers is called numeration. Our common notation started in India about 2000 years ago. The Arabs took it to Europe. Therefore these symbols are called Arabic numerals. You know that there are nine of these numerals besides the zero, which is also called naught or cipher. 4. Periods. When more than three figures are used in an integer they are separated into groups of three so as to be read more easily. The groups are called periods. For example, 1,397,352, sometimes printed as 1 397 352. 5. Separatrix. The comma used in separating periods is often called a separatrix. 6. Place value. The value of a period and of a figure depends upon the place it occupies. Therefore each has a place value. Such definitions as the above need not be memorized. The teacher should, however, be sure that the terms and the ideas which they suggest are understood. |