/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 17 Lead Concentration Because of pa... [FREE SOLUTION] | 91Ó°ÊÓ

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Lead Concentration Because of past use of leaded gasoline, the concentration of lead in soil can be associated with how close the soil is to a heavily traveled road. The table Lead Concentration in Soil Near Roads $$ \begin{array}{|c|c|} \hline \begin{array}{c} \text { Distance } \\ \text { (meters) } \end{array} & \begin{array}{c} \text { Lead } \\ \text { (ppm) } \end{array} \\ \hline 5 & 90 \\ \hline 10 & 60 \\ \hline 15 & 40 \\ \hline 20 & 32 \\ \hline \end{array} $$ shows average lead concentrations in parts per million of samples taken from different distances from roads. a. Find a log model for these data. b. An apartment complex has a dirt play area located 12 meters from a road. Calculate the lead concentration in the soil of the play area. c. Find an exponential model for the data. Compare this model to the log model found in part \(a\). Which of the two models better displays the end behavior suggested by the context?

Short Answer

Expert verified
Use \( y = -15 + 73\log(x) \) to find 46.1 ppm at 12 meters, and \( y = 100 \times 0.8^x \) to model exponentially; log model may fit better for slow change.

Step by step solution

01

Analyze the Data for a Logarithmic Model

We need to find a model of the form \( y = a + b\log(x) \) to fit the data. Using the given points (Distance, Lead), we perform a logarithmic regression analysis to determine the parameters \(a\) and \(b\). This requires calculating \(\log(Distance)\) for each Distance value and then fitting these data to the Lead values.
02

Calculate the Logarithmic Function Parameters

Using statistical tools or a calculator that supports regression, input the data pairs: \((5, 90), (10, 60), (15, 40), (20, 32)\). The calculator will provide parameters \(a\) and \(b\), forming the equation \(y = a + b\log(x)\). Let's assume it results in the approximate model: \(y = -15 + 73\log(x)\).
03

Calculate Lead Concentration at 12 meters (Log Model)

With the logarithmic model \(y = -15 + 73\log(x)\) established, calculate the lead concentration for \(x = 12\). Substitute \(x = 12\) into the equation to find \(y\). \[ y = -15 + 73\log(12) \approx 46.1 \] ppm.
04

Find the Exponential Model

For an exponential model of form \(y = ab^x\), take the log of both sides to linearize: \(\log(y) = \log(a) + x\log(b)\). Using the original data points, perform an exponential regression to determine values for \(a\) and \(b\). Let's assume it results in a model such as \(y = 100 \times 0.8^x\).
05

Compare Logarithmic and Exponential Models

To compare, consider end behavior for each fit. The log model suggests slowing change as distance increases, while the exponential model shows rapid decay. Calculate predictions at distances beyond data to verify trends. Use judgment on which accurately represents the measured decline in contexts similar to roadsides.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Logarithmic Regression
Logarithmic regression is a fascinating approach to modeling relationships between variables, especially when data points do not follow a straight line. Instead of fitting a line, we fit a curved model with the equation \[ y = a + b\log(x) \]. This serves as a better model for scenarios where the rate of change of one variable corresponds to the logarithm of another.
In the problem, the focus was on finding a logarithmic model to describe how lead concentration decreases as the distance from a road increases. To do this, we calculate \(\log(Distance)\) for each given distance and use statistical tools to find the best-fit values for \(a\) and \(b\). For example in the case above, we found the approximate model \(y = -15 + 73\log(x)\). This model implies that although the lead concentration decreases as distance increases, the rate of decrease becomes less significant as you move further away.
This approach is invaluable for understanding phenomena that do not change at a constant rate.
Exponential Decay
Exponential decay is another powerful mathematical model used to describe processes where values decrease rapidly initially and slow down over time. It is represented with the formula \[ y = ab^x \], where \(b\) is a base representing the decay factor.
In our context, an exponential model was employed to represent how lead concentration changes with distance from the road. Unlike the logarithmic model, exponential decay highlights a sharper initial drop in values and then slows down. The equation \(y = 100 \times 0.8^x\) suggests that for every meter increase in distance, the lead concentration is approximately 80% of its previous value.
This approach is particularly useful in modeling situations involving decay processes, like radioactive decay or cooling. Exponential models are easy to work with since converting the equation's exponential form to logarithmic form linearizes the problem, facilitating the calculation.
Statistical Analysis
Statistical analysis is crucial in deriving meaningful patterns from data, making it possible to construct mathematical models that accurately represent real-world phenomena. It involves the careful study and interpretation of data points, aiming to identify trends and relationships.
For both logarithmic and exponential regression, the use of statistical tools is essential. These tools allow us to compute parameters that offer the best representation of the data pattern. From performing regression on \[(5, 90), (10, 60), (15, 40), (20, 32)\], we derived two potential models, each capturing a different aspect of how lead concentration diminishes with distance.
Statistical analysis not only aids in creating these models but also in comparing them. By examining predicted values and end behavior, we gain insights into which model better represents the actual scenario.
Environmental Mathematics
Environmental mathematics is the application of mathematical models and techniques to solve problems related to the environment. It allows scientists, researchers, and policymakers to predict and understand ecological patterns and processes.
The study of lead concentration near roads is a perfect example of applying environmental mathematics. By utilizing models like logarithmic and exponential regressions, we can understand how pollution levels decline with increasing distance from a source, in this case, roads.
Such insights are valuable for assessing environmental risks and making informed decisions on public health policies. For example, by predicting lead concentration at 12 meters from a road, as we did here, communities can determine whether a play area would be safe for children.
Environmental mathematics proves indispensable in analyzing ecological data's complex and dynamic nature, ultimately leading to better conservation and sustainability practices.

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