Quadratic growth
International calls
A company providing international phone services
published the following rates for calls between the US and East Asia:
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Price for the first minute: $1.
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Price for each additional minute: 2 cents less
than for the previous minute.
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Mrs. Turner from New York phones her son in Tokyo once a week.
Their conversation sometimes lasts only a few minutes, at other times
it lasts almost half an hour. At the end of each phone call
Mrs. Turner computes the cost of the call.
In time, Mrs. Turner discovered a rule of thumb that helps her
compute the cost of a phone call quickly: she calculates
the average of the price of the first ($1) and last minutes
of her call and multiplies this average by the number of minutes
the call lasted.
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Use Mrs. Turner's rule of thumb
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Use the Quadratic growth tool to
present a function describing the dependence of the cost of a call on its duration in minutes.
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Show Mrs. Turner's rule of thumb in action through an example.
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Use Mrs. Turner's rule of thumb to construct a
correspondence rule for a function describing the dependence
of the cost of a call on its duration.
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A competing phone company offers a rate in which
the first minute costs $1.20 and each additional minute costs
3 cents less than the previous minute. Do you advise
Mrs. Turner to use the services of the other company?
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