Math Problem Statement

You are making a frame of uniform width for a picture that is to be displayed at the local museum. The picture is 3.25 feet tall and 3 feet wide. The museum has allocated 15 square feet of wall space to display the picture. What should the width of the frame be in order to use all of the allocated space?

Solution

The problem involves finding the uniform width xx of the picture frame so that the total area (including the picture and the frame) equals the allocated space of 15 square feet.

Given:

  • The dimensions of the picture are 3.25ft×3ft3.25 \, \text{ft} \times 3 \, \text{ft}.
  • The total allocated area is 15 square feet.
  • The frame has a uniform width xx.

Step-by-step solution:

  1. Picture dimensions with the frame:
    The overall dimensions of the picture including the frame will be:

    • Height: 3.25+2x3.25 + 2x (frame added to top and bottom).
    • Width: 3+2x3 + 2x (frame added to both sides).
  2. Total area equation:
    The area of the entire frame and picture is: (3.25+2x)(3+2x)=15(3.25 + 2x)(3 + 2x) = 15

  3. Expand the equation: (3.25+2x)(3+2x)=9.75+6.5x+6x+4x2(3.25 + 2x)(3 + 2x) = 9.75 + 6.5x + 6x + 4x^2 Simplify the terms: 4x2+12.5x+9.75=154x^2 + 12.5x + 9.75 = 15

  4. Set the equation to 0: Subtract 15 from both sides: 4x2+12.5x+9.7515=04x^2 + 12.5x + 9.75 - 15 = 0 4x2+12.5x5.25=04x^2 + 12.5x - 5.25 = 0

  5. Solve the quadratic equation: Use the quadratic formula: x=b±b24ac2ax = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a} Here, a=4a = 4, b=12.5b = 12.5, and c=5.25c = -5.25.

    First, calculate the discriminant: b24ac=12.524(4)(5.25)=156.25+84=240.25b^2 - 4ac = 12.5^2 - 4(4)(-5.25) = 156.25 + 84 = 240.25

    Now, calculate xx: x=12.5±240.258x = \frac{-12.5 \pm \sqrt{240.25}}{8} 240.2515.5\sqrt{240.25} \approx 15.5 x=12.5±15.58x = \frac{-12.5 \pm 15.5}{8}

    So, the two solutions are: x=12.5+15.58=38=0.375ftx = \frac{-12.5 + 15.5}{8} = \frac{3}{8} = 0.375 \, \text{ft} x=12.515.58=288=3.5(not a valid solution, since width cannot be negative)x = \frac{-12.5 - 15.5}{8} = \frac{-28}{8} = -3.5 \, (\text{not a valid solution, since width cannot be negative})

Thus, the width of the frame is 0.375 feet.


Would you like more details or have any questions?

Related Questions:

  1. How would the solution change if the picture's size were doubled?
  2. What happens if the allocated area is increased to 20 square feet?
  3. How does the quadratic formula work for negative discriminants?
  4. Can you solve this problem graphically?
  5. How would the solution change if the frame were not uniform in width?

Tip:

When solving word problems involving areas and dimensions, it's helpful to first express all quantities (like the total area) as equations before simplifying.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Area Calculation

Formulas

Quadratic equation: ax^2 + bx + c = 0
Area of a rectangle: width * height

Theorems

Quadratic formula

Suitable Grade Level

Grades 9-11