Math Problem Statement
Question 4
Exam-style question
A rectangular garden measuring 15×18 (metres) needs to have a path made around it.
The path has the same width on each side of the garden.
This is shown in the diagram:
The builder only has enough material to build a path of total area of 150 m2.
Find the width of the path (in m) if he uses up all the materials he has.
Enter your answer as a decimal, correct to three significant figures. Do not include the unit with your answer.
Solution
To solve this problem, we need to set up an equation based on the given information:
- The original rectangular garden has dimensions 15 m by 18 m.
- A path of equal width is built around the garden, and the total area of the path is 150 m².
- We are asked to find the width of the path.
Step 1: Define the variable
Let the width of the path be meters.
Step 2: Set up the dimensions of the new, larger rectangle
The path surrounds the garden, so it adds meters to each side of the garden. The new dimensions of the rectangle, including the path, will be:
- Length: (since the path adds meters on both sides of the length).
- Width: (since the path adds meters on both sides of the width).
Step 3: Calculate the area of the new, larger rectangle
The area of the larger rectangle is:
Step 4: Subtract the area of the original garden
The area of the garden without the path is: The area of the path is the difference between the area of the larger rectangle and the area of the original garden: We are told that the area of the path is 150 m²:
Step 5: Solve the equation
Expand the left-hand side: Substitute this into the equation: Simplifying: Rearrange the equation:
Step 6: Solve the quadratic equation
To solve , we can use the quadratic formula: For the equation , we have , , and .
Substitute these values into the quadratic formula:
Now solve for the two possible values for :
Since the width of the path cannot be negative, we discard and keep .
Final Answer:
The width of the path is 2.03 meters (rounded to three significant figures).
Would you like a detailed breakdown of any step? Here are some follow-up questions:
- How does the quadratic formula work in this context?
- What would happen if the area of the path was larger or smaller?
- How could you model this problem with a different shape, like a circular garden?
- How would the problem change if the path had varying widths along different sides?
- Can you explain how to solve quadratic equations in general?
Tip: Always check for physical meaning in your solutions. Negative values may be mathematically correct but don't always fit real-world contexts!
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Math Problem Analysis
Mathematical Concepts
Algebra
Quadratic Equations
Area of Rectangles
Formulas
Area of rectangle = Length × Width
Quadratic equation formula ax^2 + bx + c = 0
Quadratic formula: x = (-b ± √(b² - 4ac)) / 2a
Theorems
Quadratic formula
Suitable Grade Level
Grades 8-10
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