Trigonometry Workbook For Dummies
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You can use the number line to demonstrate simple addition and subtraction. These first steps in math become a lot more concrete with a visual aid. Here’s the main thing to remember:

  • As you go right, the numbers go up, which is addition (+).

  • As you go left, the numbers go down, which is subtraction (–).

For example, 2 + 3 means you start at 2 and jump up 3 spaces to 5, as illustrated in the below figure.


As another example, 6 – 4 means start at 6 and jump down 4 spaces to 2. That is, 6 – 4 = 2, as shown in the following figure.


You can use these simple up and down rules repeatedly to solve a longer string of added and subtracted numbers. For example, 3 + 1 – 2 + 4 – 3 – 2 means 3, up 1, down 2, up 4, down 3, and down 2. In this case, the number line would show you that 3 + 1 – 2 + 4 – 3 – 2 = 1.

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Mary Jane Sterling taught algebra, business calculus, geometry, and finite mathematics at Bradley University in Peoria, Illinois, for more than 30 years. She is the author of several For Dummies books, including Algebra Workbook For Dummies, Algebra II For Dummies, and Algebra II Workbook For Dummies.

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