
Prof. S. Brick Math 120
Summer ’02 Applied Calculus; Exam 2 section 11
Note: Be sure to read each problem completely. Show all your work. Justify all your
answers. Do the problems in order in your bluebook.
1. Algebraically find the two inflection points of y=e−x2. Sketch a graph showing them.
2. Suppose demand is given by q= 500 −10p. Is demand elastic or inelastic at p= $20 ?
How should you change the price if you want to increase revenue ?
3. Suppose the surge function y= 10te−0.25tmodels the concentration (in mg/l) of the drug
mathsmartatol. Suppose the drug is effective provided the concentration is at least 7 mg/l.
Use your graphing calculator to find the approximated values of the time coordinates that
bound the region of drug effectiveness. Sketch the graph.
4. Using the right-hand rule with 4 evenly-spaced rectangles set up (but do not compute)
the Riemann sum for Rπ
0sin(x)dx. Sketch a graph showing the rectangles. Also, using the
Fundamental theorem find the exact value of the integral.
5. Suppose a toy rocket is launched into the air from the ground. Its flight is a path 100 feet
straight up and then down and lasts, from start to finish, a total of 5 seconds. If v(t) is its
velocity where upwards is postive and downwards is negative, explain why R5
0v(t)dt = 0.
6. Find and classify the critical points of f(x) given the graph of f0(x):
7. You sell tickets for an exciting math lecture (wow!!). If you charge $20 you sell 1000
tickets. Each dollar increase in price results in 100 fewer sales. What price results in
maximum revenue ? (Use techniques from class. Do not just make up a table of values.)
8. Suppose cost in thousands of dollars is given by C(q) = q3
−12q2+ 60qwhere qis
quantity in thousands of items. Determine whether or not at q= 2 production be increased
or decreased in order to lower average cost. Draw a graph of C(q) illustrating the key fact
about marginal cost versus the average cost at q= 2.
9. Suppose the ecosystem of an island has carrying capacity of 700 rabbits. If 350 rabbits
are introduced, sketch a possible logistic model for the population as a function of time.
10. Find the derivative of f(x) = 2x5+ 2π5
x·ln(x).