Trigonometry Workbook For Dummies
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You can use a Cartesian graph to solve certain types of math problems. When you draw two lines that represent different parts of a word problem, the point at which the lines intersect (where they cross) is your answer.

Here’s an example:

Jacob is exactly 5 years younger than Marnie, and together their ages add up to 15. How old are they?

To solve this problem, first make a chart to show that Jacob is 5 years younger than Marnie:


Then make another chart to show that together, the two children’s ages add up to 15:


Finally, plot both lines on a graph where the horizontal axis represents Jacob’s age and the vertical axis represents Marnie’s age:


Notice that the two lines cross at the point where Jacob is 5 and Marnie is 10 years old, so these are the two children’s ages.

About This Article

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About the book author:

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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