Select the correct answer.

\begin{tabular}{|c|c|}
\hline
\begin{tabular}{c}
Time \\
(weeks)
\end{tabular} & \begin{tabular}{c}
Lake Depth \\
(feet)
\end{tabular} \\
\hline
0 & 346.0 \\
\hline
2 & 344.8 \\
\hline
5 & 343.0 \\
\hline
7 & 341.8 \\
\hline
10 & 340.0 \\
\hline
12 & 338.8 \\
\hline
\end{tabular}

An environmental agency studying the effects of drought on a lake found that the water level decreased at a constant rate during the first few months of the drought. When the agency began its research, the depth of the lake was 346 feet. The table represents the agency's subsequent observations about the lake's depth.

Which equation represents the depth of the lake, [tex]$y$[/tex], based on the number of weeks passed, [tex]$x$[/tex]?

A. [tex]$y = -0.6x + 346$[/tex]

B. [tex]$y = -12x + 346$[/tex]

C. [tex]$y = -0.6x$[/tex]

D. [tex]$y = -12x$[/tex]



Answer :

To determine the correct equation that represents the depth of the lake [tex]\( y \)[/tex] based on the number of weeks passed [tex]\( x \)[/tex], we will perform a linear regression analysis to derive the equation of the line that best fits the given data points.

### Step-by-Step Analysis:

1. Initial Setup:
We have the following pairs of data points [tex]$(x, y)$[/tex] where [tex]\( x \)[/tex] is the number of weeks and [tex]\( y \)[/tex] is the lake depth in feet:
[tex]\[ \begin{array}{|c|c|} \hline \text{Time (weeks)} & \text{Lake Depth (feet)} \\ \hline 0 & 346.0 \\ \hline 2 & 344.8 \\ \hline 5 & 343.0 \\ \hline 7 & 341.8 \\ \hline 10 & 340.0 \\ \hline 12 & 338.8 \\ \hline \end{array} \][/tex]

2. Determine the Equation of the Line:
- First, we need to find the slope ([tex]\( m \)[/tex]) and the y-intercept ([tex]\( b \)[/tex]) of the line in the form [tex]\( y = mx + b \)[/tex].

3. Calculate the Slope:
- The slope [tex]\( m \)[/tex] can be calculated using the formula:
[tex]\[ m = \frac{\Delta y}{\Delta x} \][/tex]
From the given data, the depth decreases steadily. To find [tex]\( \Delta y \)[/tex] (change in depth) and [tex]\( \Delta x \)[/tex] (change in weeks), let’s consider the change from 0 weeks to 2 weeks:
[tex]\[ m = \frac{344.8 - 346.0}{2 - 0} = \frac{-1.2}{2} = -0.6 \][/tex]

4. Determine the y-Intercept:
- The y-intercept [tex]\( b \)[/tex] is the depth of the lake when [tex]\( x = 0 \)[/tex]:
[tex]\[ b = 346 \][/tex]

5. Construct the Equation:
- Using the slope and y-intercept calculated:
[tex]\[ y = -0.6x + 346 \][/tex]

### Conclusion:
The equation that best represents the relationship between the lake's depth [tex]\( y \)[/tex] and the number of weeks [tex]\( x \)[/tex] is:
[tex]\[ \boxed{y = -0.6x + 346} \][/tex]

Thus, the correct answer is option A.

Other Questions