Math 162

Math 162

Quiz 3


Show all work in a neat and organized fashion. Clearly indicate your answers.

10 points possible.


Units, Units, Units! Label all numeric answers. With models, give a concise explanation of the variables.


Example: Suppose a problem asks for a model, and suppose this is the answer:
Tax = 2538.90 + 540.37t dollars, where t is the number of years since 1989.
To receive full credit, this answer must include all of the following:

(1) the correct model (i.e., Tax = 2538.90 + 540.37t),

(2) the correct label for the output (i.e., ``dollars''), and

(3) the correct explanation of the input variable (i.e., ``where t is the number of years since 1989'').



Example: Here is another correct way to write the same answer.
D = 2538.90 + 540.37x, where D= dollars of tax, and x= number of years since 1989.





1. (2 pts.) The total payroll for all city governments in the United States during a certain month can be modeled by
Payroll = 485.2 x + 5739.1 million dollars
where x is the number of years since 1990. What is the rate of change of the payroll amount? Include correct units.

2. (5 pts.) The price of an appliance is given in the table below.


          Price   
   Year       (dollars)   
             
             
   1977       85   
   1979       92   
   1981       108   
   1983       126   
   1985       135   
   1987       159   
   1989       161   
   1991       187   


(a) Find a linear model for the price of the appliance. Do not round.

(b) Use the model to predict the price in 1986. Round your answer.

(c) Suppose the linear increase continues, and use the model to predict when the price will be $300. Round your answer.

3. (3 pts.) If a country has a growth rate of 2.3 percent per year, how many years will it take for that country's population to double? Use an exponential model, and please round your answer to 3 decimal places.



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