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The rate of change of annual U.S. factory sales (in billions of dollars per year) of consumer electronic goods to dealers from 1990 through 2001 can be modeled as \(s(t)=0.12 t^{2}-t+5.7\) billion dollars per year where \(t\) is the number of years since 1990 . (Sources: Based on data from Statistical Abstract, 2001 ; and Consumer Electronics Association) a. Use a limit of sums to estimate the change in factory sales from 1990 through 2001 . b. Write the definite integral symbol for this limit of sums. c. If factory sales were \(\$ 43.0\) billion in 1990 , what were they in \(2001 ?\)

Short Answer

Expert verified
The factory sales in 2001 were approximately $107.46 billion.

Step by step solution

01

Set up the integral for the rate of change

We want to find the change in factory sales from 1990 to 2001. We start by using the given function \( s(t) = 0.12t^2 - t + 5.7 \). To find the total change, we need to integrate this rate of change function over the interval \( t = 0 \) to \( t = 11 \) (since 2001 is 11 years after 1990).
02

Write the definite integral

The definite integral \( \int_{0}^{11} s(t) \, dt \) will give us the total change in sales over the specified period. In terms of a limit of sums, this integral represents the limit as the number of subintervals goes to infinity, summing up small changes in sales over each subinterval.
03

Evaluate the integral

We integrate \( s(t) = 0.12t^2 - t + 5.7 \) from 0 to 11: \[ \int_{0}^{11} (0.12t^2 - t + 5.7) \, dt = \left[ 0.04t^3 - \frac{1}{2}t^2 + 5.7t \right]_{0}^{11} \].Substituting the limits, we compute: \[ \left( 0.04(11)^3 - \frac{1}{2}(11)^2 + 5.7 \times 11 \right) - \left( 0.04(0)^3 - \frac{1}{2}(0)^2 + 5.7 \times 0 \right). \] This simplifies to approximately \( 64.46 \) billion dollars.
04

Calculate factory sales in 2001

Given the factory sales in 1990 were \\(43 billion, and the total change over the period is approximately \\)64.46 billion, the factory sales in 2001 can be calculated by adding the 1990 sales to the total change:\[ 43 + 64.46 = 107.46 \] billion dollars.

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Key Concepts

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

Rate of Change
In mathematics, the rate of change measures how a quantity changes over time. In our exercise, we're looking at the rate of change in factory sales. Imagine it as tracking the speed at which sales grow from year to year. Each year, the sales numbers tell us how much more (or less) was sold compared to the previous year.

For us, this rate is given by the function \( s(t) = 0.12t^2 - t + 5.7 \), where \( t \) represents the number of years after 1990. This equation helps in forecasting how factory sales will change.

Key points of understanding include:
  • The rate of change function can be a polynomial like ours.
  • It helps predict the future sales trend for each year.
  • This function allows us to calculate overall changes over a specific period.
Understanding the rate of change here means being able to predict how the factory's sales are increasing or decreasing year by year over time.
Definite Integral
The concept of the definite integral is tied to finding the exact total change over a specific interval. Think of it as adding up an infinite number of tiny changes to get the exact total.

In our case, the definite integral of the function \( s(t) \) from 0 to 11 gives us the total change in factory sales between 1990 and 2001. This is written as \( \int_{0}^{11} (0.12t^2 - t + 5.7) \, dt \). Here, \( 0 \) to \( 11 \) represents the time period.

Benefits of using definite integrals:
  • They provide a precise sum of all little changes.
  • The integral gives the total change in a specified interval, without estimating.
  • Integral symbols \( \int \) and \( dt \) are standard in measurements of change.
Integrals turn many small quantities into a single meaningful total, essential for accurate analysis.
Limit of Sums
At its core, a limit of sums connects to the idea of adding up countless little parts to get a total. This is foundational in calculus and is essentially what a definite integral accomplishes.

When we apply a limit of sums to our factory sales example, we visualize breaking down the interval from 1990 to 2001 into many tiny pieces. Then, we calculate the change in sales for each tiny interval and sum these up. As the number of intervals increases, the approximation becomes exact—this is the essence of integrating over the limits of 0 and 11.

Here's why the limit of sums is important:
  • It forms the basic principle of integration.
  • It transforms approximate methods into exact calculations by scaling to infinity.
  • It's essential for obtaining precise results in real-world data analysis.
Understanding limits of sums allows one to see how calculus builds precise totals from many small parts.
Factory Sales Modeling
Factory Sales Modeling involves using mathematical functions to represent and predict real-world sales data over time. In this example, our model is centered around the sales figures for consumer electronics goods.

The function \( s(t) = 0.12t^2 - t + 5.7 \) acts as a sales model, representing how sales increase or decrease over time, starting from 1990. It helps in exploring outcomes like future sales estimates and assessing past performance.

Why factory sales modeling is beneficial:
  • It provides a structured way to analyze sales trends over years.
  • The model helps in forecasting future sales based on historical data.
  • Using models, businesses can make informed decisions on production and marketing.
With factory sales modeling, businesses can plan and strategize effectively, armed with clear data-driven insights.

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