Question

part i - multiple choice: circle the response that best completes the statement or answers the question. then write the letter of your answer in the table after problem 7.

1. (5 points) the table below shows the median monthly electricity bill (in tens of dollars) for households in a city from january 2015 to january 2021, where t is years since the start of 2015. compute the average rate of change of the bill from the start of 2017 to the start of 2021.

year t (years after 2015)	0	1	2	3	4	5	6
bill (tens of us $)	12	13.2	14.5	15.5	16.4	17.5	18.1

a. from the start of 2017 to the start of 2021, the bill increased by 0.5 tens of dollars per year, on average.
b. from the start of 2017 to the start of 2021, the bill increased by 0.5 tens of dollars per year, on average.
c. from the start of 2017 to the start of 2021, the bill decreased by 0.6 tens of dollars per year, on average.
d. from the start of 2017 to the start of 2021, the bill increased by 0.75 tens of dollars per year, on average.
e. from the start of 2017 to the start of 2021, the bill increased by 0.9 tens of dollars per year, on average.
e. from the start of 2017 to the start of 2021, the bill decreased by 1.2 tens of dollars per year, on average.

1. (5 points) a bacterial culture (in

Explanation:

Step1: Identify start - end values

In 2017 ($t = 2$), the bill is $14.5$ (tens of dollars). In 2021 ($t = 6$), the bill is $18.1$ (tens of dollars).

Step2: Use average rate of change formula

The average rate of change formula is $\frac{y_2 - y_1}{x_2 - x_1}$. Here, $y$ is the bill amount and $x$ is the year. So, $\frac{18.1 - 14.5}{6 - 2}=\frac{3.6}{4}=0.9$.

Answer:

E. From the start of 2017 to the start of 2021, the bill increased by 0.9 tens of dollars per year, on average.