Concept explainers
Reminder Round all answers to two decimal places unless otherwise indicated.
8. Cell Phone Charges One cell phone plan charges a flat monthly rate of
a. Choose letters to represent the variables.
b. Write a formula to express the cell phone charges as a function of the number of text messages (assume that the number is at least
c. Use functional notation to show the cost of the cell phone if you have
d. Write the formula to express the cell phone charges, this assuming that the number of text messages is less than
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EBK FUNCTIONS AND CHANGE: A MODELING AP
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- Earnings Reynalda works as a salesperson in the electronics division of a department store. She earns a base weekly salary plus a commission based on the retail price of the goods she has sold. If she sells x dollars’ worth of goods in a week, her earnings for that week are given by the function E(x)=400+0.03x (a) Find E(2000) and E(15,000) . (b) What do your answers in part (a) represent? (c) Find E(0) . What does this number represent? (d) Find the net change and the average rate of change of her earnings E between x=2000 and x=15,000 . (e) From the formula for E, determine what percentage Reynalda earns on the goods that she sells.arrow_forwardVital Statistics Let bt be the number of births in the United States in year t, and let dt represent the number of deaths in the United States in year t, where t=10 corresponds to 2010. (a) If pt is the population of the United States in year t, find the function ct that represents the percent change in the population of the United States. (b) Interpret c16.arrow_forwardApplications Set up and solve the required proportion. Heat dissipation The power, in watts, dissipated as heat in a resistor varies directly with the square of the voltage and inversely with the resistance. If 20 volts are placed across a 20-ohm resistor, it will dissipate 20 watts. What voltage across a 10-ohm resistor will dissipate 40 watts?arrow_forward
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