Math Problem Statement

A​ person's rectangular dog pen for his dog must have an area of 300 square feet.​ Also, the length must be 10 feet longer than the width. Find the dimensions of the pen. ? ? Question content area bottom Part 1 The width of the pen

Solution

Let the width of the pen be denoted by ww feet. Since the length is 10 feet longer than the width, the length can be written as w+10w + 10 feet.

The area of a rectangle is given by:

Area=length×width\text{Area} = \text{length} \times \text{width}

Given that the area of the pen is 300 square feet, we can set up the following equation:

w×(w+10)=300w \times (w + 10) = 300

Now, expand the equation:

w2+10w=300w^2 + 10w = 300

Subtract 300 from both sides to set the equation to zero:

w2+10w300=0w^2 + 10w - 300 = 0

This is a quadratic equation. We can solve it using the quadratic formula:

w=b±b24ac2aw = \frac{-b \pm \sqrt{b^2 - 4ac}}{2a}

For the equation w2+10w300=0w^2 + 10w - 300 = 0, the coefficients are a=1a = 1, b=10b = 10, and c=300c = -300. Plug these values into the quadratic formula:

w=10±1024(1)(300)2(1)w = \frac{-10 \pm \sqrt{10^2 - 4(1)(-300)}}{2(1)}

w=10±100+12002w = \frac{-10 \pm \sqrt{100 + 1200}}{2}

w=10±13002w = \frac{-10 \pm \sqrt{1300}}{2}

w=10±36.062w = \frac{-10 \pm 36.06}{2}

Now, calculate the two possible values for ww:

w=10+36.062orw=1036.062w = \frac{-10 + 36.06}{2} \quad \text{or} \quad w = \frac{-10 - 36.06}{2}

w=26.062=13.03(positive solution)w = \frac{26.06}{2} = 13.03 \quad \text{(positive solution)}

w=46.062=23.03(negative solution, not possible since width cannot be negative)w = \frac{-46.06}{2} = -23.03 \quad \text{(negative solution, not possible since width cannot be negative)}

Thus, the width of the pen is approximately 13 feet.

Now, the length is 10 feet longer than the width:

Length=13+10=23 feet\text{Length} = 13 + 10 = 23 \text{ feet}

So, the dimensions of the pen are approximately:

  • Width: 13 feet
  • Length: 23 feet

Would you like more details or have any questions?


Here are 5 questions related to this topic:

  1. How do we derive the quadratic formula?
  2. What are other methods to solve quadratic equations?
  3. How would the problem change if the area was different?
  4. What are the properties of quadratic functions?
  5. Can we solve the same problem graphically?

Tip: Always check if a quadratic equation has real solutions by first evaluating the discriminant b24acb^2 - 4ac. If the discriminant is negative, there are no real solutions.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Area of a Rectangle

Formulas

Area of rectangle = length × width
Quadratic formula: w = (-b ± √(b² - 4ac)) / 2a

Theorems

Quadratic Formula

Suitable Grade Level

Grades 8-10