Question

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 $9.95 10 $10.65 20 $11.35 30 $12.05 40 $12.75 The average rate of change is $1.30, meaning that for each minute of talk time, the monthly bill increases by $1.30. The average rate of change is $0.07, meaning that for each minute of talk time, the monthly bill increases by $0.07. The average rate of change is $1.30, meaning that for every ten minutes of talk time, the monthly bill increases by $1.30. The average rate of change is $0.07, meaning that for every ten minutes of talk time, the monthly bill increases by $0.07.

Answer 1

We can use the first and the last point of the table to find the average rate of change during the 40-minute talk time.

At t=0, the charges are $ 9.95
at t=40, the charges are $12.75

Average rate of change from t=0 to t=40 can be calculated as:

$\frac{12.75-9.95}{40-0} =0.07$

This means, the average rate of change is $0.07, meaning that for each minute of talk time, the monthly bill increases by $0.07. (Option B)