Math Problem Statement

In quadrilateral ABCD, AB || DC and AD 1 AB. Also, AB = 8 m, DC = BC =5 m. Find the area of the quadrilateral.

[Hint: ABCD is a trapezium and AD is the height. Let CE || AD meet AB in E. CE = √52-32 m = 4 m]

Solution

The given quadrilateral ABCD is a trapezium because ABDCAB \parallel DC and ADAD is perpendicular to ABAB, meaning ADAD is the height of the trapezium.

Step-by-step solution:

  1. Given Data:

    • AB=8mAB = 8 \, \text{m} (parallel side),
    • DC=5mDC = 5 \, \text{m} (parallel side),
    • BC=5mBC = 5 \, \text{m},
    • ADABAD \perp AB (height),
    • CEADCE \parallel AD with CE=4mCE = 4 \, \text{m}.
  2. Understand the Trapezium Geometry: Since ADABAD \perp AB and ABDCAB \parallel DC, we know that ADAD is the height of the trapezium. We can visualize the trapezium as two parallel sides ABAB and DCDC, with the non-parallel sides ADAD and BCBC. The length of ADAD, which is the perpendicular height, is needed.

  3. Using the Hint:

    • The hint tells us CE=5232m=4mCE = \sqrt{52 - 32} \, \text{m} = 4 \, \text{m}, which gives us the height AD=CE=4mAD = CE = 4 \, \text{m}.
  4. Area of the Trapezium: The formula for the area of a trapezium is:

    Area=12×(Sum of parallel sides)×Height\text{Area} = \frac{1}{2} \times ( \text{Sum of parallel sides} ) \times \text{Height}

    Substituting the values:

    Area=12×(AB+DC)×AD\text{Area} = \frac{1}{2} \times (AB + DC) \times AD Area=12×(8+5)×4\text{Area} = \frac{1}{2} \times (8 + 5) \times 4 Area=12×13×4=26m2\text{Area} = \frac{1}{2} \times 13 \times 4 = 26 \, \text{m}^2

Thus, the area of the quadrilateral ABCDABCD is 26m226 \, \text{m}^2.


Would you like further details or clarification on any step?

Here are 5 related questions for further exploration:

  1. What is the formula for the perimeter of a trapezium?
  2. How do you find the height in a trapezium if it's not given?
  3. What are the properties of a trapezium compared to other quadrilaterals?
  4. Can the area of a trapezium be found using diagonals?
  5. How do we determine the type of trapezium (isosceles, right, etc.)?

Tip: Always remember to check for perpendicularity when identifying heights in quadrilaterals, especially trapeziums!

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Math Problem Analysis

Mathematical Concepts

Geometry
Trapezium
Area of Quadrilateral

Formulas

Area of a trapezium = (1/2) × (Sum of parallel sides) × Height

Theorems

Properties of trapezium

Suitable Grade Level

Grades 8-10