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Fall 2017 Final Exam
PREDICT 400: Math for Modelers
Points possible: 100
Description: The final exam will cover topics from sessions 1-9.
Resources: The exam is completely open book. You may use course textbooks, materials
provided on Canvas, graphing calculators (such as TI 83 or 84); but any more advanced
calculators, Excel Solver, Web calculators, Web-graphic calculators, or simplex method
calculators are not allowed. Programming languages other than Python are also not permitted.
For questions that require calculations, all calculations should be shown, not just the final
answer. This will allow for partial credit for those answers that might be set up correctly but
have calculation errors. If variables are introduced, whether in a program or in a mathematical
solution, you will need to explicitly state what the variables represent and clearly state the
results based on the variable designations.
For questions that specifically require Python, your code and output should be included to
constitute work shown along with solutions. For questions that require graphs, only use Python.
Python can be used for all questions unless instructed otherwise. For any problem the uses
Python, your code and output must be provided.
Restrictions: All answers are to be your work only. You are not to receive assistance from any
other person.
To complete the exam:
1. Answer all questions on the exam thoroughly. Create a single Microsoft Word document,
including the question number, the question, your typed answer, and graphs if required. You
may use Word’s equation editor to complete your answers.
2. Once you have completed your exam, save the file with a meaningful filename such as “Final”
followed by your last name and return to the exam item where you downloaded the exam PDF,
click View/Complete Assignment, and submit your document.
1. A local copy center needs to buy white paper and yellow paper. They can buy from
three suppliers. Supplier 1 sells a package of 20 reams of white and 10 reams of yellow
for $60. Supplier 2 sells a package of 10 reams of white and 10 reams of yellow for $40.
Supplier 3 sells a package of 10 reams of white and 20 reams of yellow for $50. The
copy center needs 350 reams of white and 400 reams of yellow. Using Python,
determine (1) how many packages they should buy from each supplier in order to
minimize cost and (2) the minimum cost.
2. A new test has been developed to detect a particular type of cancer. A medical
researcher selects a random sample of 1,000 adults and finds (by other means) that 4%
have this type of cancer. Each of the 1,000 adults is given the new test and it is found
that the test indicates cancer in 99% of those who have it and in 1% of those who do
not. Based on these results, what is the probability of a randomly chosen person having
cancer given that the test indicates cancer? What is the probability of a person having
cancer given that the test does not indicate cancer?Round the probabilities to four
decimal places.
3. If a tank holds 5000 gallons of water, which drains from the bottom of the tank in 40
minutes, then the volume of the water remaining in the tank after 𝑡 minutes is given by
𝑡
2
𝑉(𝑡) = 5000 (1 − 40) , 0 ≤ 𝑡 ≤ 40. Using Python, determine the rate at which water
is draining from the tank. When will it be draining the fastest?
4. A rectangular container with a volume of 475 ft3 is to be constructed with a square base
and top. The cost per square foot for the bottom is $0.20, for the top is $0.10, and for
the sides is $0.015. Find the dimensions of the container that minimize the cost. Round
to two decimal places.
5. Assume the total revenue from the sale of 𝑥 items is given by 𝑅(𝑥) = 27 ln(6𝑥 + 1)
while the total cost to produce 𝑥 items is 𝐶(𝑥) = 𝑥⁄7. Find the approximate number of
items that should be manufactured so that profit is maximized. Justify that the number
of items you found gives you the maximum and state what the maximum profit is.
6. For the following function, determine the domain, critical points, intervals where the
function is increasing or decreasing, inflection points, intervals of concavity, intercepts,
and asymptotes where applicable. Use this information and Python to graph the
function.
𝑓(𝑥) = −
1
+4
(𝑥 + 2)2
7. The rate of growth of the profit (in millions) from an invention is approximated by the
2
function 𝑃′ (𝑥) = 𝑥𝑒 −𝑥 where 𝑥 represents time measured in years. The total profit in
year two that the invention is in operation is $25,000. Find the total profit function.
Round to three decimals.
8. For a certain drug, the rate of reaction in appropriate units is given by
𝑅 ′ (𝑡) =
6
1
+
𝑡 + 1 √𝑡 + 1
where 𝑡 is time (in hours) after the drug is administered. Find the total reaction to the
drug from 1 to 8 hours after it is administered.Round to two decimal places.
9. Determine if the following function is a probability density function on [0, ∞).
𝑥 3⁄ , 𝑖𝑓 0 ≤ 𝑥 ≤ 2
𝑓(𝑥) = { 8
4⁄ , 𝑖𝑓 𝑥 > 2
𝑥3
If it is a probability density function, then calculate𝑃(1 ≤ 𝑥 ≤ 5) and round to four
decimal places. If it is not, explain why.
10. Researchers have shown that the number of successive dry days thatoccur after a
rainstorm for a particular region is a random variable that is distributed exponentially
with a mean of 9 days. Using Python, determine the (separate) probabilities that 13 or
more successive dry days occur after a rainstorm, and fewer than 2 dry days occur after
a rainstorm. Round the probabilities to four decimal places.