Math Problem Statement

A stained-glass window is being designed in the shape of a rectangle surmounted by a semicircle, as shown in the figure. The width of the window is to be 3 feet, but the height his yet to be determined. If 26 ft? of glass is to be used, find the height h.

Solution

We need to find the height hh of a stained-glass window that is shaped like a rectangle surmounted by a semicircle. The width of the window is given as 3 feet, and the total area of the glass is 26 square feet.

Step-by-Step Process:

  1. Define the components of the window:

    • The width of the window is given as 33 feet.
    • The height hh represents the vertical height of the rectangular portion of the window.
    • The semicircle sits on top of the rectangle, and its diameter equals the width of the window, i.e., 33 feet.
  2. Area of the rectangular portion: The area ArectA_{\text{rect}} of the rectangular part of the window is given by: Arect=width×height=3×h=3hA_{\text{rect}} = \text{width} \times \text{height} = 3 \times h = 3h

  3. Area of the semicircular portion: The diameter of the semicircle is 3 feet, so the radius rr of the semicircle is: r=32=1.5 feetr = \frac{3}{2} = 1.5 \text{ feet} The area AsemiA_{\text{semi}} of the semicircle is half the area of a full circle, which is given by: Asemi=12×πr2=12×π(1.5)2=12×π×2.25=1.125πA_{\text{semi}} = \frac{1}{2} \times \pi r^2 = \frac{1}{2} \times \pi (1.5)^2 = \frac{1}{2} \times \pi \times 2.25 = 1.125\pi

  4. Total area of the window: The total area AtotalA_{\text{total}} is the sum of the areas of the rectangle and the semicircle: Atotal=Arect+Asemi=3h+1.125πA_{\text{total}} = A_{\text{rect}} + A_{\text{semi}} = 3h + 1.125\pi

  5. Set up the equation: The total area of the window is given as 26 square feet. Therefore, we can set up the following equation: 3h+1.125π=263h + 1.125\pi = 26 Solving for hh, we first subtract the area of the semicircle from both sides: 3h=261.125π3h = 26 - 1.125\pi

  6. Approximate the value of π\pi: Using π3.1416\pi \approx 3.1416, we can calculate the right-hand side: 3h=261.125×3.1416=263.534=22.4663h = 26 - 1.125 \times 3.1416 = 26 - 3.534 = 22.466

  7. Solve for hh: Finally, divide both sides by 3 to find hh: h=22.46637.489h = \frac{22.466}{3} \approx 7.489

Thus, the height of the rectangular portion of the window is approximately h7.49h \approx 7.49 feet.

Would you like further details or have any questions?

Related Questions:

  1. How would the height change if the total area of the glass were increased to 30 square feet?
  2. What would be the height if the width of the window were 4 feet instead of 3 feet?
  3. How can we find the radius of the semicircle given the total area and width?
  4. If the window had a different shape, like an ellipse on top, how would the calculations change?
  5. What is the exact area of the semicircular part, without approximating π\pi?

Tip:

When solving geometry problems, breaking the figure into simpler shapes and calculating their areas individually helps streamline the solution process.

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Math Problem Analysis

Mathematical Concepts

Geometry
Area Calculation
Algebra

Formulas

Area of a rectangle: A = width * height
Area of a semicircle: A = (1/2) * π * r^2
Total area: A_total = A_rect + A_semi

Theorems

Area calculation for composite shapes

Suitable Grade Level

Grades 9-10