Читать книгу Basic Math & Pre-Algebra All-in-One For Dummies (+ Chapter Quizzes Online) - Mark Zegarelli - Страница 19

Here’s an old question whose answer may surprise you: Suppose you took a job that paid you just 1 penny the first day, 2 pennies the second day, 4 pennies the third day, and so on, doubling the amount every day, like this:

As you can see, in the first ten days of work, you would’ve earned a little more than $10 (actually, $10.23 — but who’s counting?). How much would you earn in 30 days? Your answer may well be, “I wouldn’t take a lousy job like that in the first place.” At first glance, this looks like a good answer, but here’s a glimpse at your second ten days’ earnings:

By the end of the second 10 days, when you add it all up, your total earnings would be over $10,000. And by the end of 30 days, your earnings would top out around $10,000,000! How does this happen? Through the magic of exponents (also called powers). Each new number in the sequence is obtained by multiplying the previous number by 2:

As you can see, the notation means multiply 2 by itself 4 times.

You can use exponents on numbers other than 2. Here’s another sequence you may be familiar with:

In this sequence, every number is 10 times greater than the number before it. You can also generate these numbers using exponents:

This sequence is important for defining place value, the basis of the decimal number system, which I discuss in Chapter 3. It also shows up when I discuss decimals in Chapter 13 and scientific notation in Chapter 17. You find out more about exponents in Chapter 5.