A cell phone plan has a monthly cost that is shown in the table below. What is the correct statement regarding the average rate of change during the 40-minute time of talk?

Total minutes of talk time Monthly cost of cell phone

0 $19.95

10 $20.45

20 $20.95

30 $21.45

40 $21.95

A.) The average rate of change is $0.50, meaning that for each minute of talk time, the monthly bill increases by $0.50.

B.) The average rate of change is $0.50, meaning that for every ten minutes of talk time, the bill increases by $0.50.

C.) The average rate of change is $0.05, meaning that for each minute of talk time, the monthly bill increases by $0.05.

D.) The average rate of change is $0.05, meaning that for every ten minutes of talk time, the bill increases by $0.05.

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haybug1228 haybug1228 · Answer 1 · 2016-08-19T18:21:38-04:00

The answer would be B The average rate of change is $0.50, meaning that for every ten minutes of talk time, the bill increases by $0.50.

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carlosego carlosego · Answer 2 · 2018-08-26T09:46:50-04:00

For this case, the first thing we must do is find the average rate of change for the mentioned interval.

By definition we have to:

$AVR = \frac{f(x2)-f(x1)}{x2-x1}$

Substituting values we have:

$AVR = \frac{21.95-19.95}{40-0}$

Rewriting we have:

$AVR = \frac{2}{40}$

$AVR = \frac{1}{20}

AVR = 0.05$

Answer:

C.) The average rate of change is $0.05, meaning that for each minute of talk time, the monthly bill increases by $0.05.