Lesson24

# Lesson24 - MA 15200 Lesson 24 Section 3.7 Certain formulas...

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1 MA 15200 Lesson 24 Section 3.7 Certain formulas are called variation models. These formulas show how one quantity changes in relation to other quantities. There are four types of variation: Direct, Inverse, Joint, and Combined. All variation formulas (variation models) involve a constant k . I Direct Variation. 13 S h = This is a direct variation formula that says the salary of a person is 13 times the hours worked. The constant k is 13 (\$13 is the hourly wage). It is easy to understand, that as the number of hours increases, so does the salary earned. The format for direct variation is y kx = . In direct variation (as long as the constant is positive) as x increases, so does y . You can also see that this model would have a graph that is a line with a positive slope of k and a y -intercept at 0. Direct Variation: If a situation is described by an equation in the form y kx = , where k is a nonzero constant, we say that y varies directly as x or y is directly proportional to x . The number k is called the constant of variation or the constant of proportionality. Steps for Solving a Direct Variation Problem: 1. Write an equation that models the given English statement. 2. Substitute the given values into the equation in step 1 and solve for k , the constant. 3.

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Lesson24 - MA 15200 Lesson 24 Section 3.7 Certain formulas...

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