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

      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 . Here’s the up and down rule:

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

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

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

      Q. Use the number line to add .

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

      Q. Use the number line to add .

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

      Q. Use the number line to add .

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

      Q.

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

      Now you can drop the plus sign and use the negative sign for subtraction:

      Q. Use the number line to subtract

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

      Q. Use the number line to subtract .

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

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

      (a)

      (b)

      (c)

      (d)

      (e)

      (f)

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

      (a)

      (b)

      (c)

      (d)

      (e)

      (f)

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

      (a)

      (b)

      (c)

      (d)

      (e) Скачать книгу