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Real-World Numbers

Here's a boiled-down version of a question from Carnegie Mellon's Lifetime Math program:

Your boss tells you to find the best deal in cellular-phone service.

Economy service is $19.95 a month plus 31 cents per minute of airtime. Silver service is $40.95 a month plus 16 cents per minute of airtime. Gold service is $80.95 a month with free airtime.

Define variables. Write equations. Make tables and graphs. Find slopes and points of intersection. For each plan, how much airtime will $100 buy? For what range of airtime is each plan cheapest?

Updated June 14, 1997 by bwwebmaster
Copyright 1996, Bloomberg L.P.
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