Shortcut Trick
Radius of circumcircle = side of inscribed regular hexagon = r
Area of circle = πr2
Area of regular hexagon = (3√3/2)r2
Uncovered Area = πr2 − (3√3/2)r2 = r2(2π − 3√3) / 2
Ratio = Area of circle ÷ Uncovered Area = 2π / (2π − 3√3)
∴ The correct answer is 2π/(2π − 3√3).
Alternate Method
Given:
A regular hexagon is inscribed in a circle.
Formula Used:
Area of a circle = πr2
Area of a regular hexagon = 6 × (√3 / 4)a2 (where a is the side length)
For a regular hexagon inscribed in a circle, the side length (a) equals the radius (r).
O
r
Shaded blue region = Area not covered by hexagon
Calculations:
⇒ Let the radius of the circle be r.
⇒ Side of the inscribed regular hexagon = r
⇒ Area of the circle = πr2
⇒ Area of the hexagon = 6 × (√3 / 4)r2 = (3√3 / 2)r2
⇒ Area not covered by hexagon = Area of circle − Area of hexagon
⇒ Area not covered = πr2 − (3√3 / 2)r2
⇒ Area not covered = r2(2π − 3√3) / 2
⇒ Required Ratio = (Area of circle) ÷ (Area not covered)
⇒ Ratio = πr2 ÷ [r2(2π − 3√3) / 2]
⇒ Ratio = 2π / (2π − 3√3)
∴ The correct answer is 2π/(2π − 3√3).
Additional Information
Circumcircle of a Regular Hexagon
The circumcenter and incenter of a regular hexagon coincide. The radius of the circumscribed circle is exactly equal to the side length of the hexagon (R = a).
Incircle of a Regular Hexagon
The radius of a circle inscribed inside a regular hexagon is given by r = (a√3)/2. The ratio of the area of the circumcircle to the incircle is 4:3.
Area of an Equilateral Triangle
A regular hexagon is composed of exactly 6 identical equilateral triangles. The area of one such triangle with side a is (√3 / 4)a2.