AB and CD are diameters. Let, AB = 2x cm ∴ Radius of circle = x cm. ∴ Area of the shaded region = (2x)2–πx2 =(4x2–πx2)sq.cm. According to the question, 4x2–πx2=42 ⇒ 4x2–
22x2
7
=42 ⇒
28x2−22x2
7
=42 ⇒ 6x2=42×7 ⇒x2=
42×7
6
=7×7 ∴ x = 7 cm. ∴ Diameter of circle = 2 × 7 = 14 cm