In Figure, AB and CD are two diameters of a circle (with centre O) perpendicular to each other and OD is the diameter of the smaller circle. If OA = 7 cm, find the area of the shaded region.

Radius of smaller circle = 7/2 cm
Area of smaller circle = πr² = π(7/2)² = 22/7 × 7/2 × 7/2 = 77/2 cm²
Radius of larger circle = 7 cm
Area of semicircle AECFB
= 1/2 × πr² = π(7)² = 1/2 × 22/7 7 × 7 = 77 cm²
Area of triangle ACB
= 1/2 × AB × OC = 1/2 × 14 × 7 = 49 cm²
Area of Shaded Region
= Area of smaller circle + Area of semicircle AECFB – Area of triangle ACB
= (77/2 + 77 – 49) cm² = (38.5 + 28) cm² = 66.5 cm²

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