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Sales growth: The total sales \(S\), in thousands of dollars, of a small firm is growing exponentially with time \(t\) (measured in years since the start of 2008). Analysis of the sales growth has given the following linear model for the natural logarithm of sales: $$ \ln S=0.049 t+2.230 \text {. } $$ a. Find an exponential model for sales. b. By what percentage do sales grow each year? c. Calculate \(S(6)\) and explain in practical terms what your answer means. d. When would you expect sales to reach a level of 12 thousand dollars?

Short Answer

Expert verified
a. Sales model: \( S(t) = 9.30 \cdot e^{0.049t} \); b. Growth: 5.02\% annually; c. \( S(6) = 12.27 \) (about $12,270 in 2014); d. Reach $12K mid-2013.

Step by step solution

01

Exponential Model for Sales

To find the exponential model for sales, start by taking the exponential of both sides of the given equation \( \ln S = 0.049t + 2.230 \). This gives \( S = e^{0.049t + 2.230} \). Simplifying, we have \( S = e^{2.230} \cdot e^{0.049t} \). Upon calculating, \( e^{2.230} \approx 9.30 \), so the exponential model is \( S(t) = 9.30 \cdot e^{0.049t} \). This represents the sales in thousands of dollars.
02

Annual Sales Growth Percentage

In an exponential model of the form \( S(t) = a \cdot e^{bt} \), the annual growth rate is \((e^b - 1) \cdot 100\%\). Here, \( b = 0.049 \), so the growth rate is \((e^{0.049} - 1) \cdot 100\%\). Calculating gives \( (1.0502 - 1) \cdot 100\% \approx 5.02\%\). Thus, sales grow by approximately 5.02\% each year.
03

Calculate Sales at Year 6

Plug \( t = 6 \) into our exponential model \( S(t) = 9.30 \cdot e^{0.049t} \): \( S(6) = 9.30 \cdot e^{0.049 \cdot 6} \approx 9.30 \cdot e^{0.294} \approx 12.27 \). So, at the start of 2014 (6 years after the start of 2008), the sales are approximately 12,270 dollars.
04

Find Year When Sales Reach $12,000

To find when sales will reach $12,000, know \( S(t) = 12 \). We set the equation \( 12 = 9.30 \cdot e^{0.049t} \). Solving for \( t \), divide both sides by 9.30: \( \frac{12}{9.30} = e^{0.049t} \approx 1.2903 \). Take the natural log of both sides to solve for \( t \): \( \ln 1.2903 = 0.049t \rightarrow t \approx \frac{\ln 1.2903}{0.049} \approx 5.61 \). Thus, sales will reach approximately 12,000 dollars halfway through year 2013 (mid-2013).

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Key Concepts

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

Sales Growth
Sales growth is all about the increase in sales over a given period. In the context of a small firm, sales growth signifies an improvement in business performance. When sales grow exponentially, it means sales figures increase not at a constant amount, but at a constant percentage rate per time period. This is crucial for businesses to understand as it reflects the potential scalability of their operations.
When analyzing sales growth, especially for firms with small starting figures, the growth can appear quite rapid if expressed in percentage terms rather than absolute numbers. This type of growth is important because it indicates how a business is developing relative to its size.
To put this into practical terms, calculating sales growth helps businesses make informed financial decisions, plan for the future, and measure success against previous performance. A steady, exponential sales growth is often a sign of a healthy business that’s expanding its customer base and increasing its market share.
Exponential Model
The exponential model is a mathematical representation used to describe how something grows over time—in this case, the sales of a business. The exponential model derived from the given data is:
\[ S(t) = 9.30 \cdot e^{0.049t} \]
This model indicates that sales start at a base amount and then grow multiplicatively over time. The expression involves the mathematical constant \(e\) (approximately equal to 2.71828), used to express continuous growth processes.
The exponential growth model is powerful for predicting future values and making estimates about when a business might reach certain milestones, such as hitting a specific sales target.
In simpler terms, the model provides a way to visualize and quantify how quickly a business is growing, given its past and current sales data.
Annual Growth Rate
The annual growth rate is a percentage that describes the average yearly increase in sales. It is derived from the exponential growth model and provides one of the most telling signs of business health.
In this exercise, the annual growth rate is calculated by:
\[ (e^{b} - 1) \times 100\% \]
where \(b\) is the growth constant from the exponential model. For this scenario, \(b = 0.049\), yielding an annual growth rate of approximately 5.02\%.
This means that the company's sales are growing by slightly more than 5\% every year, suggesting a steady upward trend.
Understanding this rate helps businesses and stakeholders to forecast long-term growth and investment potential, and to set realistic goals for expansion.
Logarithmic Equation
Logarithmic equations are used to transform exponential relationships into linear ones, making them easier to handle and interpret. This transformation is particularly useful when dealing with exponential growth, as it simplifies complex calculations.
The original exercise started with a logarithmic equation:
\[ \ln S = 0.049t + 2.230 \]
This depicts the natural logarithm \(\ln\) of the sales, which is a linear function of time \(t\). By using this linear equation, we extracted the exponential model, bridging the gap between logarithmic and exponential expressions.
In business and economics, logarithmic equations are instrumental for understanding growth trends. They help simplify exponential growth models to analyze variables more straightforwardly, providing clearer insights into how changes over time affect sales and other metrics. This makes it easier for decision-makers to make informed choices based on historical data and trend projections.

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Most popular questions from this chapter

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