/*! 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 34 The death rate per 100,000 popul... [FREE SOLUTION] | 91Ó°ÊÓ

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The death rate per 100,000 population \(y\) in year \(x\) for heart discase and cancer is approximated by these equations: $$\begin{array}{lc}\text {Heart Disease:} & 6.9 x+2 y=728.4 \\\\\text {Cancer:} & -1.3 x+y=167.5 \end{array}$$where \(x=0\) corresponds to \(1970 .^{*}\) If the equations remain accurate, when will the death rates for heart disease and cancer be the same?

Short Answer

Expert verified
Answer: The death rates for heart disease and cancer will be the same around the year 2011.

Step by step solution

01

Set up the equations

We are given the following linear equations: $$ \begin{array}{lc}\text {Heart Disease:} & 6.9x +2y=728.4 \\ \\ \text{Cancer:} & -1.3x +y=167.5 \end{array} $$ The problem is asking us to find the value of x that represents the year when both death rates will be equal, which implies \(y_{Heart \ Disease} = y_{Cancer}\). Therefore, we can solve the system of linear equations to find the solution.
02

Elimination method

To solve the system of linear equations, we can use the elimination method. In this case, we will eliminate y (death rate) to find x (year). First, we need to multiply the second equation with coefficient 2, so that both equations will have the same coefficient for y: $$ \begin{array}{lc} \text {New Cancer Equation:} & (-1.3\times2)x +(2\times 1)y=2\times 167.5 \end{array} $$ This results in: $$ \begin{array}{lc} \text {New Cancer Equation:} & -2.6x + 2y = 335 \end{array} $$
03

Subtracting Cancer equation from Heart Disease equation

Now we can subtract the new cancer equation from the heart disease equation to eliminate y from the system: $$ (6.9 x+2 y) - (-2.6 x+2 y)=728.4-335 $$ $$ 9.5x=393.4 $$
04

Solve for x

Now we can find the value of x by dividing by 9.5: $$ x=\frac{393.4}{9.5} $$ $$ x\approx41.4 $$
05

Find the year

Since x represents the years past 1970, we need to add the value of x to 1970 to find the year when the death rates for heart disease and cancer will be the same: $$ 1970 + 41.4 \approx 2011.4 $$ The death rates for heart disease and cancer will be the same around the year 2011.

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Key Concepts

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

Elimination Method
Understanding the Elimination Method is a crucial part of solving systems of linear equations. This method involves removing one of the variables, allowing the remaining variable to be easily solved.

The core idea is to adjust the equations so that one variable can be canceled out when the equations are combined. Here’s how it works:
  • Select a variable to eliminate. It’s often strategic to choose the variable that will simplify your work. In our example, both equations have the variable 'y' on similar scales, making 'y' a good choice to eliminate.
  • Multiply the equations by necessary constants so that when you add or subtract them, one variable will cancel out. For instance, to eliminate 'y', the coefficients of 'y' in both equations must be the same or additive inverses.
  • Combine the equations by addition or subtraction to eliminate the chosen variable, leaving a simpler equation with one variable.
  • Solve for the remaining variable, which is often a straightforward calculation.
This method is particularly useful when coefficients are manipulated to simplify the system and bring clarity to solutions.
Linear Algebra
Linear Algebra provides the theoretical framework to handle and solve linear systems like the ones seen in this exercise. Linear equations express relationships of equality and often consist of variables multiplied by constants. In our exercise, the equations model heart disease and cancer death rates.

Fundamentally, linear algebra treats these equations as straight lines in a coordinate system. When these lines intersect, the intersection point represents the solution to the equations, which in our situation is when the death rates for both diseases become equal.
  • The intersection point is crucial as it gives actual real-world data, like when trends will converge.
  • Linear algebra not only helps to solve such systems but also provides insights into their properties, such as existence and uniqueness of solutions.
Understanding linear algebra concepts allows you to move beyond simple arithmetic and explore more complex relationships and patterns, critical in fields such as engineering, economics, and various sciences.
Mathematical Modeling
Mathematical Modeling is the process of using mathematics to represent, analyze, and predict real-world phenomena. In the exercise, linear equations are used to model death rates due to heart disease and cancer over time.

By establishing a mathematical model, we can:
  • Predict future values by evaluating the model equations with given or estimated inputs.
  • Simulate different scenarios to test theories or potential outcomes, such as policy changes or health initiatives.
  • Gain a deeper understanding of trends and behaviors in data over time, supporting decision-making and planning.
In this instance, mathematical modeling provides a systematic approach to understanding health trends, making it a vital tool for researchers and policymakers aiming to improve public health. By refining models with more data or updated parameters, these predictions become increasingly accurate and beneficial for strategic planning.

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Most popular questions from this chapter

In Exercises \(21-36,\) solve the system. $$\begin{array}{rr} x+7 y-z+2 w= & 24 \\ 5 x-3 y-8 z & =7 \\ x+4 y+7 z+w= & 6 \\ 3 y+4 z-w= & -2 \end{array}$$

A store sells their 80 -GB iPods for \(\$ 350,\) and their \(30-\mathrm{GB}\) iPods for \(\$ 250 .\) Their total iPod inventory would sell for \(\$ 15,250 .\) During a recent month, the store actually sold half of the 80 -GB iPods and two-thirds of their 30 -GB iPods, taking in a total of \(\$ 9,000 .\) How many of each kind did they have at the beginning of the month?

Solve the system by any method. $$\begin{aligned} x+y+\quad 2 w &=3 \\ 2 x-y+z-w &=5 \\ 3 x+3 y+2 z-2 w &=0 \\ x+2 y+z &=2 \end{aligned}$$

Bill and Ann plan to install a heating system for their swimming pool. since gas is not available, they have a choice of electric or solar heat. They have gathered the following cost information.$$\begin{array}{|l|c|c|}\hline \text { System } & \begin{array}{c}\text { Installation } \\\\\text { Costs }\end{array} & \begin{array}{c}\text { Monthly } \\\\\text { Operational cost }\end{array} \\\\\hline \text { Electric } & \$ 2,000 & \$ 80 \\\\\hline \text { Solar } & \$ 14,000 & \$ 9.50 \\\\\hline\end{array}$$ (a) Ignoring changes in fuel prices, write a linear equation for each heating system that expresses its total cost \(y\) in terms of the number of years \(x\) of operation. (b) What is the five-year total cost of electric heat? Of solar heat? (c) In what year will the total cost of the two heating systems be the same? Which is the cheaper system before that time? After that time?

The table shows the number of passenger cars (in thousands) imported into the United States from Japan and Canada in selected years.$$\begin{array}{|l|l|c|c|c|c|c|}\hline \text { Year } & 1995 & 1996 & 1997 & 1998 & 1999 & 2000 \\\\\hline \text { Japan } & 1114.4 & 1190.9 & 1387.8 & 1456.1 & 1707.3 & 1839.1 \\\\\hline \text { Canada } & 1552.7 & 1690.7 & 1731.2 & 1837.6 & 2170.4 & 2138.8 \\\\\hline\end{array}$$ (a) Use linear regression to find an equation that approximates the number \(y\) of cars imported from Japan in year \(x,\) with \(x=5\) corresponding to 1995 (b) Do part (a) for Canada. (c) If these models remain accurate, in what year will the imports from Japan and Canada be the same? Approximately how many cars will be imported that year?

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