Chapter 7: Problem 48
Explain what is meant by joint variation. Give an example with your explanation.
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Chapter 7: Problem 48
Explain what is meant by joint variation. Give an example with your explanation.
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Will help you prepare for the material covered in the first section of the next chapter. Evaluate \(5 x+7\) for \(x=a+h\)
Without showing the details, explain how to solve the formula $$ \frac{1}{R}=\frac{1}{R_{1}}+\frac{1}{R_{2}} $$ for \(R_{1}\). (The formula is used in electronics.)
Two formulas that approximate the dosage of a drug prescribed for children are $$ \begin{aligned} \text { Young's rule: } & C=\frac{D A}{A+12} \\ \text { and Cowling's rule: } & C=\frac{D(A+1)}{24} \end{aligned} $$ In each formula, \(A=\) the child's age, in years, \(D=\) an adult dosage, and \(C=\) the proper child's dosage. The formulas apply for ages 2 through \(13,\) inclusive. Use the formulas to solve Exercises \(93-96\) For a 12 -year-old child, what is the difference in the dosage given by Cowling's rule and Young's rule? Express the answer as a single rational expression in terms of \(D\) Then describe what your answer means in terms of the variables in the models.
A company that manufactures wheelchairs has fixed costs of \(\$ 500,000 .\) The average cost per wheelchair, \(C,\) for the company to manufacture \(x\) wheelchairs per month is modeled by the formula $$ C=\frac{400 x+500,000}{x} $$ Use this mathematical model to solve Exercises \(69-70\). How many wheelchairs per month can be produced at an average cost of \(\$ 450\) per wheelchair?
Exercises \(123-125\) will help you prepare for the material covered in the next section. Multiply and simplify: \(\quad x y\left(\frac{1}{x}+\frac{1}{y}\right)\)
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