Math Problem Statement

The length of the rectangle is 6 cm less than the width. Find the perimeter of a rectangle if its area is 112 square meters

Solution

Let the width of the rectangle be denoted by ww (in meters), and the length is given as l=w6l = w - 6 meters.

The area of a rectangle is calculated by the formula:

Area=Length×Width\text{Area} = \text{Length} \times \text{Width}

Given that the area is 112 square meters, we can set up the equation:

(w6)×w=112(w - 6) \times w = 112

Expanding the equation:

w26w=112w^2 - 6w = 112

Rearranging it into a standard quadratic form:

w26w112=0w^2 - 6w - 112 = 0

Now, solving this quadratic equation using the quadratic formula:

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

Here, a=1a = 1, b=6b = -6, and c=112c = -112. Substituting these values:

w=(6)±(6)24(1)(112)2(1)w = \frac{-(-6) \pm \sqrt{(-6)^2 - 4(1)(-112)}}{2(1)}

w=6±36+4482w = \frac{6 \pm \sqrt{36 + 448}}{2}

w=6±4842w = \frac{6 \pm \sqrt{484}}{2}

w=6±222w = \frac{6 \pm 22}{2}

So, the two possible solutions for ww are:

w=6+222=282=14w = \frac{6 + 22}{2} = \frac{28}{2} = 14 w=6222=162=8(which is not a valid solution since width cannot be negative)w = \frac{6 - 22}{2} = \frac{-16}{2} = -8 \quad (\text{which is not a valid solution since width cannot be negative})

Thus, the width is w=14w = 14 meters, and the length is:

l=w6=146=8 metersl = w - 6 = 14 - 6 = 8 \text{ meters}

Now, the perimeter PP of the rectangle is given by the formula:

P=2×(Length+Width)P = 2 \times (\text{Length} + \text{Width})

Substituting the values:

P=2×(14+8)=2×22=44 metersP = 2 \times (14 + 8) = 2 \times 22 = 44 \text{ meters}

Therefore, the perimeter of the rectangle is 44 meters.

Would you like more details or have any questions?

Here are 5 related questions to expand your understanding:

  1. How would the problem change if the length was 6 cm more than the width?
  2. How do you solve quadratic equations graphically?
  3. What are other methods to solve quadratic equations besides the quadratic formula?
  4. How do you derive the formula for the area of different shapes?
  5. How does the perimeter change if both the length and width are doubled?

Tip: When solving word problems, always define variables clearly and check the units carefully to avoid confusion.

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Math Problem Analysis

Mathematical Concepts

Algebra
Quadratic Equations
Geometry

Formulas

Area of a rectangle: Area = Length × Width
Perimeter of a rectangle: P = 2 × (Length + Width)
Quadratic formula: w = (-b ± √(b^2 - 4ac)) / 2a

Theorems

Quadratic formula

Suitable Grade Level

Grades 8-10