Math CentralQuandaries & Queries


Question from John, a student:


AT&T charges $39.99 for 450 minutes per month. It charges 45 cents per minute over the 450 minutes.
How can I make a piecewise equation of this problem?

Hi John,

I would draw a graph with minutes on the horizontal axis and monthly charge on the vertical axis. From minutes = 0 to minutes = 450 the graph is a horizontal line at monthly charge = $39.99. At this point the line slopes upwards so that for each additional minute beyond 450 there is an added cost of $0.45.


My graph isn't to scale.


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