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Given the data points , , and , fit an exponential function of the form to the data. Show your work and explain how you determined the values of and .
A biologist is studying the growth of a bacterial colony. The population of the bacteria doubles every hour. If the initial population is 100 bacteria, write an exponential function to model the population growth and predict the population after 5 hours.
A certain radioactive substance decays according to the function , where is the initial quantity and is the decay constant. If the initial quantity is 500 grams and the quantity reduces to 250 grams in 3 hours, find the decay constant .
A car depreciates in value according to the function , where is the initial value and is the depreciation constant. If a car is worth $20,000 initially and $15,000 after 2 years, determine the depreciation constant .
A population of fish in a lake grows according to the function , where is the initial population and is the growth rate. If the initial population is 200 fish and the population grows to 400 fish in 5 years, find the growth rate .
Given a dataset of bacteria growth over time, describe how you would determine if an exponential model is a good fit for the data. Include the steps you would take and the criteria you would use to assess the goodness of fit.
Explain how you would refine an exponential model if the initial fit is not satisfactory. What steps would you take to improve the model?
Describe how you would use residual plots to assess the goodness of fit for an exponential model. What patterns would you look for?
How would you use the method of least squares to fit an exponential model to a given dataset? Describe the process briefly.
A researcher fits an exponential model to a dataset and finds that the model underestimates the data at higher values of the independent variable. What steps can the researcher take to refine the model?
A population of bacteria doubles every 3 hours. If you start with 100 bacteria, how many bacteria will there be after 12 hours? Show your work.
A car depreciates in value by 15% each year. If the car was originally worth $20,000, what will its value be after 5 years? Show your work.
A certain radioactive substance has a half-life of 10 years. If you start with 200 grams of the substance, how much will remain after 30 years? Show your work.
An investment account earns 5% interest compounded annually. If you invest $1,000, how much will the account be worth after 10 years? Show your work.
A certain species of fish in a lake has a population that grows at a rate of 8% per year. If the current population is 5,000 fish, what will the population be in 7 years? Show your work.
A certain radioactive substance decays according to the function , where is the initial quantity and is the decay constant. If the initial quantity is 500 grams and the quantity reduces to 250 grams in 3 hours, find the decay constant .
(Student response here)
Given and , we substitute into the decay function: . Dividing both sides by 500, we get . Taking the natural logarithm of both sides, we get . Solving for , we get .
If the decay constant is approximately 0.231, what is the quantity of the substance after 6 hours?