CAT 2024 Slot 3 QA Question 3

Multiple choice (+3 / −1) · Geometry · Circles · Try it, then check the answer and solution below.

A circular plot of land is divided into two regions by a chord of length 10310\sqrt{3} meters such that the chord subtends an angle of 120∘120^\circ at the center. Then, the area, in square meters, of the smaller region is
Answer and solution

Answer: C) 25(4π3−3)25 \left(\frac{4\pi}{3} - \sqrt{3}\right)

📌 Core Concept
The problem involves finding the area of a smaller segment of a circle divided by a chord. The key concepts are the relationship between the chord length, radius, and central angle, as well as the formulas for the area of a sector and the area of a triangle.
🔢 Step-by-Step Solution
1
Find the Radius (r):
The chord length formula is:
Chord length=2rsin⁡(θ2)Giventhechordlengthis103metersandthecentralangleθ=120∘:103=2rsin⁡(60∘)Sincesin⁡(60∘)=32:103=2r⋅32  ⟹  103=r3  ⟹  r=10 meters\text{Chord length} = 2r \sin\left(\frac{\theta}{2}\right) Given the chord length is 10\sqrt{3} meters and the central angle \theta = 120^\circ: 10\sqrt{3} = 2r \sin(60^\circ) Since \sin(60^\circ) = \frac{\sqrt{3}}{2}: 10\sqrt{3} = 2r \cdot \frac{\sqrt{3}}{2} \implies 10\sqrt{3} = r\sqrt{3} \implies r = 10 \text{ meters}
2
Calculate the Area of the Sector:
The area of a sector with central angle

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