Select all solutions to . Be prepared to explain your reasoning.
Select all solutions to . Be prepared to explain your reasoning.
3.2
Activity
Moon Base Population
In a video game, Jada is building a moon base to support a growing population and to deal with challenges. Jada’s base has a population of 54,500 in the year 2240, and between 2240 and 2270 the population of the base grows exponentially by about 60% per decade.
Find the population of Jada’s moon base in 2250 and in 2260 according to this model.
The population is a function of the number of decades after 2240. Write an equation for .
Explain what means in this situation.
Graph your function using graphing technology, and estimate the value of .
Explain why we can find the value of by multiplying 54,500 by . Find that value.
Based on the model, what was the population of Jada’s base in 2258? Show your reasoning.
3.3
Activity
Cleaning Up a Spill
A chemical is accidentally spilled into a lake and needs to be cleaned up. The cleaning process decreases the amount of the chemical in the lake roughly exponentially. Here is a graph representing , an exponential function that models the amount of chemical left in the lake, hours after the cleaning begins.
Use the graph to estimate , and explain what it tells us in this situation.
After one hour, 0.75 liters of the chemical remains in the lake. Find an equation that defines .
Student Lesson Summary
Some exponential functions can have inputs that are any numbers on the number line, not just integers.
Suppose the area of a pond covered by algae , in square meters, is modeled by , where is the number of weeks since a treatment was applied to the pond. How could we use this equation to determine the area covered after 1 day?
Well, since is one week and each week has 7 days, is 1 day. So after 1 day, the algae covers square meters, or about 181 square meters. Using a calculator, we know that the expression , which is equivalent to , is about 0.906. This means that after 1 day, only 91% of the algae from the previous day remains.
This information can also be seen on a graph representing the area. The point at marks the area covered by the algae after 1 week. Point marks the covered area after of a week, or one day.
The graph can be used to estimate the vertical coordinate of and shows that it is close to 180.
Glossary
None
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