The Mathematics of Money

(Darren Dugan) #1

Copyright © 2008, The McGraw-Hill Companies, Inc.



  1. By investing in an improved telecommunications system, a call center believes it can save $350,000 per year in costs
    each year for the foreseeable future. If the company requires a 7.25% rate of return, what is the present value of this
    cost savings? If the new system would cost $2,500,000, is it fi nancially justifi ed by this savings?


C. Projections with Increasing Payments


  1. Find the present value of a perpetuity of $5,000 per year, increasing by 4% annually, assuming the required rate of return is 12%.

  2. Find the present value of a perpetuity of $7,250 per year, increasing by 5% annually, assuming the required rate of
    ret urn is 8%.

  3. A company is considering building a small hydroelectric plant. The plant would produce a profi t of $72,500 in the fi rst
    year, and the company believes that electric prices will rise in the future, so this profi t will grow 5% per year. The company
    requires an 8% rate of return. The plant can be expected to continue producing power for the foreseeable future. What is
    the largest cost to build this facility that these projections would justify?

  4. According to a guidance counselor, someone with a college degree can be expected to earn $15,000 per year more in
    her fi rst year after graduation than someone who does not have a degree, and this difference grows by 7% each year.
    Suppose that you require an 8% rate of return on your investments.


a. Use a perpetuity to estimate the present value of the projected additional earnings from having a college degree.
According to this, is graduating from college fi nancially worth the effort and expense?
b. Instead of using a perpetuity, suppose that you assume a 40-year working career. Calculate the present value of
$15,000 per year for 40 years, assuming the same rate you used in part a. How does this affect your conclusion?

D. Grab Bag


  1. Suppose you have the choice of two investments:



  • Part ownership of a landscape company. You project your share of the profi ts will be $12,000 in the fi rst year, and will
    increase by 2% annually.

  • Part ownership of a property management company. You project your share of profi ts will be $12,000 in the fi rst year
    and will increase by 5% annually.


You would require a 12% return from either of these investments. The landscape company would require a $125,000
investment; the property management company would require a $150,000 investment. Calculate the net present value
of each of these opportunities. On the basis of their net present values, which opportunity is the more attractive?


  1. Mohan is considering investing in a business that he projects would earn him profi t of $35,000 in the fi rst year. He requires an
    11% rate of return. Using perpetuities, calculate the present value of these profi ts, assuming they are growing at a rate of:


a. 1%
b. 3%
c. 5%
d. 8%
e. Does the trend in these values agree with common sense?

Exercises 14.1 571
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