Question

Due to the increase of posts on social media, the number of flip cell phones is in exponential decline. Data collected from 2009 to 2014 shows the estimated number of flip phones amongst Washington State high school students.

Years (since 2009) 0 1 2 3 4

Number of Flip Phones 256 192 144 108 81
(in thousands)


Write an equation in two variables to represent this situation. Let x represent the number years since 2009 and y represent the total number of flip phones (in thousands) owned by high school students in Washington.

Answer 1

`y=256e^(-0.288x)`

where y is in thousands

Explanation:

The equation in two variables that can be used to represent the situation given can be determined using computer software such Stat-Crunch or Ms. Excel or advanced calculators.

I shall use Ms. Excel for this question.

In Ms. Excel, enter the data into any two adjacent columns. Next, highlight the data, then click the insert ribbon and select the scatter-plot option.

Excel returns a scatter-plot chart as shown in the attachment below.

After obtaining the scatter-plot, we shall need to add a trend line in order to determine the mathematical equation that best fits the scenario given.

Click anywhere inside the chart, then select the design tab under chart tools. Click on the Add Chart element in the upper left corner of the excel workbook and select more trend-line options. This feature will enable us to fit any trend-line to our data.

Select the exponential option, since we were informed that he number of flip cell phones is in exponential decline,ensuring you check the box; Display Equation on chart.

Find the attached.

The equation in two variables is thus;

`y=256e^(-0.288x)`