Basic Math & Pre-Algebra All-in-One For Dummies (+ Chapter Quizzes Online). Mark Zegarelli
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Название: Basic Math & Pre-Algebra All-in-One For Dummies (+ Chapter Quizzes Online)

Автор: Mark Zegarelli

Издательство: John Wiley & Sons Limited

Жанр: Математика

Серия:

isbn: 9781119867265

isbn:

СКАЧАТЬ add and subtract negative numbers on the number line. Don’t worry about memorizing every little bit of this procedure. Instead, just follow along so you get a sense of how negative numbers fit onto the number line. (If you need a quick refresher on how the number line works, see Chapter 1.)

      Starting with a negative number

      When you’re adding and subtracting on the number line, starting with a negative number isn’t much different from starting with a positive number. For example, suppose you want to calculate math. Using the up and down rule, you start at math and go up math:

An illustration of negative numbers on the number line. math

      Similarly, suppose you want to calculate math. Again, the up and down rule helps you out. You’re subtracting, so move to the left: start at math, down math:

An illustration of negative numbers on the number line. math

      .

      Adding a negative number

      Suppose you want to calculate math. You already know to start at math, but where do you go from there? Here’s the up and down rule for adding a negative number:

      Remember Adding a negative number is the same as subtracting a positive number — go down on the number line.

An illustration of negative numbers on the number line. math

      Tip If you rewrite a subtraction problem as an addition problem — for instance, rewriting math you can use the commutative and associative properties of addition, which I discuss earlier in this chapter. Just remember to keep the negative sign attached to the number when you rearrange the problem: math.

      Subtracting a negative number

      The last rule you need to know is how to subtract a negative number. For example, suppose you want to calculate math. Here’s the up and down rule:

      Remember Subtracting a negative number is the same as adding a positive number — go up on the number line.

      This rule tells you that math is the same as math, so start at math:

An illustration of negative numbers on the number line. math

      Tip When subtracting negative numbers, you can think of the two negative signs canceling each other out to create a positive.

      ExampleQ. Use the number line to add math.

      A. 2. On the number line, math means math which brings you to 2:

      Q. Use the number line to add math.

      A. 4. On the number line, math means start at 6, down 2, which brings you to 4:

An illustration of negative numbers on the number line.

      Q. Use the number line to add math.

      A. −7. On the number line, math means math which brings you to −7:

An illustration of negative numbers on the number line.

      Q. math

      A. 16. Switch around the two numbers with the signs attached:

math

      Now you can drop СКАЧАТЬ