What is the area of the given figure?
Aptitude
Area
Difficulty: Medium
Choose an option
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A98.8 cm²
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B110.4 cm²
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C120 cm²
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D132.6 cm²
Answer
Correct Answer: 110.4 cm²
Explanation
### Concept & Composite Area
To find the area of a composite figure, break it down into simpler geometric shapes (rectangles and triangles).
The figure consists of a central rectangle and two right-angled triangles attached at the ends. We use the Pythagorean theorem to find missing side lengths.
Pythagorean theorem: $$a^2 + b^2 = c^2$$
### Step-by-Step Solution
* **Given:** A central rectangle with length 12 cm. Two right-angled triangles at the ends with legs of 4 cm and 6 cm.
* **Analyze the Triangles:** The right angle symbol indicates the legs are 4 cm and 6 cm.
Area of one triangle = $\frac{1}{2} \times 4 \times 6 = 12 \text{ cm}^2$.
Total area for two triangles = $12 \times 2 = 24 \text{ cm}^2$.
* **Find Rectangle Width:** The hypotenuse of these right triangles forms the width of the central rectangle.
$\text{Width} = \sqrt{4^2 + 6^2} = \sqrt{16 + 36} = \sqrt{52}$ cm.
$\sqrt{52} \approx 7.21$ cm (or typically approximated as 7.2 in such problems).
* **Calculate Rectangle Area:**
Area = $\text{Length} \times \text{Width} = 12 \times \sqrt{52} \approx 12 \times 7.2 = 86.4 \text{ cm}^2$.
* **Total Area:**
Total Area = Rectangle Area + Triangles Area = $86.4 + 24 = 110.4 \text{ cm}^2$.
### Exam Strategy & Shortcut
Recognize that $\sqrt{52}$ is slightly larger than $\sqrt{49}$ (which is 7). $12 \times 7 = 84$. Total area is slightly more than $84 + 24 = 108$. Looking at the options, $110.4 \text{ cm}^2$ is the only logical choice that perfectly aligns with a standard approximation of $\sqrt{52} \approx 7.2$.
### Common Pitfall
Misidentifying the hypotenuse. If one assumes the 6 cm side is the hypotenuse instead of a leg, the calculations will lead to an incorrect and missing option. Always pay close attention to where the right-angle square symbol is placed.
### Final Answer
Therefore, the correct answer is **110.4 cm²**.