LITMIR.BIZ

Chapter 3

      Counting on Success: Numbers and Digits

      IN THIS CHAPTER

       Understanding how place value turns digits into numbers

       Distinguishing whether zeros are important placeholders or meaningless leading zeros

       Reading and writing long numbers

       Understanding how to round numbers and estimate values

      When you’re counting, ten seems to be a natural stopping point — a nice, round number. The fact that our ten fingers match up so nicely with numbers may seem like a happy accident. But of course, it’s no accident at all. Fingers were the first calculator that humans possessed. Our number system — the Hindu-Arabic numbers, also called the decimal numbers — is based on the number ten because humans have 10 fingers instead of 8 or 12. In fact, the very word digit has two meanings: numerical symbol and finger.

      In this chapter, I show you how place value turns digits into numbers. I also show you when 0 is an important placeholder in a number and why leading zeros don’t change the value of a number. And I show you how to read and write long numbers. After that, I discuss two important skills: rounding numbers and estimating values.

      TELLING THE DIFFERENCE BETWEEN NUMBERS AND DIGITS

      Sometimes people confuse numbers and digits. For the record, here’s the difference:

      For example, 7 is both a digit and a number. In fact, it’s a one-digit number. However, 15 is a string of two digits, so it’s a number — a two-digit number. And 426 is a three-digit number. You get the idea.

In a sense, a digit is like a letter of the alphabet. By themselves, the uses of 26 letters, A through Z, are limited. (How much can you do with a single letter such as K or W?) Only when you begin using strings of letters as building blocks to spell words does the power of letters become apparent. Similarly, the ten digits, 0 through 9, have limited usefulness until you begin building strings of digits — that is, numbers.

Knowing Your Place Value

      The number system you’re most familiar with — Hindu-Arabic numbers — has ten familiar digits: