Question
Quantitative Aptitude Question on Mensuration
A chord of length 5 cm subtends an angle of 60° at the centre of a circle. The length, in cm, of a chord that subtends an angle of 120° at the centre of the same circle is
A
8
B
6√2
C
5√3
D
2π
Answer
5√3
Explanation
Solution
The correct answer is (C):
Since ΔOAB is equilateral,
radius of the circle is 5 cm.
In ΔOCD, by sine rule,
5/sin30° = CD/sin120°
⇒ CD= 5√3/2×2
= 5√3