The figure above shows the number of emails sent per day plotted against the number of hours an adult works on a computer per day. Which of the following best estimates the average rate of change in the number of emails sent compared to the number of hours working on a computer?

Options

A. `0.12`
B. `1.5`
C. `8.5`
D. `12`

Answer

C

Explanation

Difficult: Medium
Category: Problem Solving and Data Analysis/ Scatterplots
Strategic Advice: When real-world data is presented in a scatterplot, the average rate of change is the same as the slope of the best-fit line.
Getting to the Answer: Find the slope of the best-fit line using the slope formula, `m=(y_(2)-y_(1))/(x_(2)-x_(2))` and any two points that lie on (or very close to ) the line. Using the two points (4, 46) and (8, 80), the average rate of change is about `(80-46)/(8-4)=(34)/(4)=8.5`, which is (C). Note that the answer choices are spread out enough that any two points along the line, even points for which you estimate the coordinates, will yield a slope that is close enough to one of the answer choices.