The area of an equilateral triangle ABC is 17320.5 cm². With each vertex of the triangle as centre, a circle is drawn with radius equal to half the length of the side of the triangle (see Figure).

Let the each side of equilateral triangle = a
Area of equilateral triangle = 17320.5 cm²
⇒ √3/4 a² = 17320.5 ⇒ 1.73205/4 a² ⇒ 17320.5 ⇒ a² = 40000 ⇒ a = 200
Area of sector ADEF
= θ/360° × πr² = 60°/360° × 22/7(100)² = 1/6 × 3.14 × 100 × 100 = 15700/3 cm²
Area of shaded region = Area of equilateral triangle – Area of three sectors
= 17320.5 cm² – 3 x 15700/3 cm²
= 17320.5 cm² – 15700 cm²
= 1620.5 cm²