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

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      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 the plus sign and use the negative sign for subtraction:

math

      Q. Use the number line to subtract math

      A. −5. On the number line, math means start at −1, down 4, which brings you to −5:

An illustration of negative numbers on the number line.

      Q. Use the number line to subtract math.

      A. −2. The expression math means start atmath (because the two negative signs cancel each other out), which brings you to math:

      5Your turn Use the number line to solve the following addition problems:

      (a) math

      (b) math

      (c) math

      (d) math

      (e) math

      (f) math

      6 Solve the following addition problems without using the number line:

      (a) math

      (b) math

      (c) math

      (d) math

      (e) math

      (f) math

      7 Use the number line to solve the following subtraction problems:

      (a) math

      (b) math

      (c) math

      (d) math

      (e) Скачать книгу