Chapter 5: Problem 82
A vegetable garden with an area of 200 square feet is to be fertilized. If the length of the garden is 1 foot less than three times the width, find the dimensions of the garden. (IMAGE CANNOT COPY)
Short Answer
Expert verified
The dimensions are 24 feet in length and \(\frac{25}{3}\) feet in width.
Step by step solution
01
Define Variables
Let's use two variables to represent the dimensions of the garden. Denote the width of the garden as \( w \) (in feet) and the length of the garden as \( l \) (in feet). Since we know that the length is 1 foot less than three times the width, we can express it as \( l = 3w - 1 \).
02
Set Up the Equation
We know that the area of the garden is 200 square feet. The area of a rectangle is given by the product of its length and width, so we have the equation: \( l \times w = 200 \). Substituting \( l = 3w - 1 \) from the previous step, we get: \((3w - 1)w = 200\).
03
Expand and Simplify the Equation
Expand \((3w - 1)w = 200\) to form a quadratic equation: \(3w^2 - w = 200\). Rearrange this to standard form: \(3w^2 - w - 200 = 0\).
04
Factorize the Quadratic Equation
We need to solve the quadratic equation \(3w^2 - w - 200 = 0\). To factorize it, find two numbers that multiply to \(-600\) (the product of \(3\) and \(-200\)) and add to \(-1\) (the coefficient of \(w\)). These numbers are \(-25\) and \(24\). The equation can be rewritten as: \(3w^2 + 24w - 25w - 200 = 0\).
05
Group Terms and Factor by Grouping
Group the terms in pairs: \((3w^2 + 24w) + (-25w - 200) = 0\). Factor each group: \(3w(w + 8) - 25(w + 8) = 0\). Notice \(w + 8\) is common, so factor it out: \((3w - 25)(w + 8) = 0\).
06
Solve for \(w\)
Set each factor equal to zero and solve for \(w\):1. \(3w - 25 = 0\) gives \(w = \frac{25}{3}\).2. \(w + 8 = 0\) gives \(w = -8\). Since a negative width is not possible, we discard it. Thus, \(w = \frac{25}{3}\).
07
Compute the Length
With \(w = \frac{25}{3}\), substitute back to find the length: \(l = 3w - 1 = 3 \times \frac{25}{3} - 1 = 24\). The length is 24 feet.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Area of a Rectangle
Calculating the area of a rectangle is foundational in geometry. It's simple: multiply the length by the width. This formula can be written as:
In this particular problem, we're given the area of the garden as 200 square feet. With the length described in terms of the width, we have the equation:
Understanding how to set up equations from word problems is key. We translate descriptive text about dimensions into a useful mathematical equation, which then becomes solvable.
- The Area, \( A \), of a rectangle = Length, \( l \), \( \times \) Width, \( w \)
In this particular problem, we're given the area of the garden as 200 square feet. With the length described in terms of the width, we have the equation:
- \( l \times w = 200 \)
Understanding how to set up equations from word problems is key. We translate descriptive text about dimensions into a useful mathematical equation, which then becomes solvable.
Factoring Quadratic Equations
A quadratic equation appears when an area calculation transforms into multiplying a length and width with additional terms. Here, after substitution, the equation became \(3w^2 - w - 200 = 0\). Moving to a standard form helps us see if the equation can be factored more easily.
Factoring involves finding two binomials that multiply to give the original quadratic equation. The process is systematic:
Factoring involves finding two binomials that multiply to give the original quadratic equation. The process is systematic:
- Multiply the leading coefficient by the constant term, which here yields \(-600\).
- Find two numbers that multiply to \(-600\) and sum to the middle term's coefficient, \(-1\).
- \(3w^2 + 24w - 25w - 200 = 0\).
- Grouping leads to \((3w + 24)(w - 25)\), where common factors let us simplify further.
Solving Equations
Once a quadratic is factorable, solving it involves setting each factor to zero. For \((3w - 25)(w + 8) = 0\), set each binomial equal to zero to find potential solutions:
- \(3w - 25 = 0\) implies \(w = \frac{25}{3}\)
- \(w + 8 = 0\) implies \(w = -8\), which isn't feasible in geometry due to negative dimensions.
- \(l = 3 \times \frac{25}{3} - 1 = 24\) feet