The circumference of a circular plot is 396 metres. what is the area of the circular plot?
Aptitude
Area
Difficulty: Medium
Choose an option
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A9446 sq. m
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B9856 sq. m
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C12474 sq. m
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D18634 sq. m
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ENone of these
Answer
Correct Answer: 12474 sq. m
Explanation
### Concept & Area from Circumference
We are given the outer boundary length. To find the enclosed space (area), we first isolate the radius from the circumference formula.
$$ \text{Circumference} = 2\pi r $$
$$ \text{Area} = \pi r^2 $$
### Step-by-Step Solution
* Given: Circumference = $396\text{ m}$.
* Set up equation: $2\pi r = 396 \Rightarrow 2 \times \frac{22}{7} \times r = 396$.
* Simplify left side: $\frac{44}{7} \times r = 396$.
* Solve for $r$: $r = \frac{396 \times 7}{44}$.
* $44$ goes into $396$ exactly $9$ times: $r = 9 \times 7 = 63\text{ m}$.
* Calculate Area: $\pi r^2 = \frac{22}{7} \times 63 \times 63$.
* Simplify: $22 \times 9 \times 63 = 198 \times 63$.
* Calculate final value: $198 \times 63 = 12474\text{ sq. m}$.
### Exam Strategy & Shortcut
Instead of doing $198 \times 63$ the long way, treat $198$ as $(200 - 2)$.
$63 \times (200 - 2) = 12600 - 126 = 12474$. This mental math trick dramatically reduces time and arithmetic errors.
### Common Pitfall
Failing to square the radius when moving from circumference to area, or accidentally squaring the diameter instead.
### Final Answer
Therefore, the correct answer is **12474 sq. m**.