Question

14. AB and CD are respectively arcs of two concentric circles of radii 21 cm and 7 cm and centre 0 (see Fig. 12.32). If ZAOB = 30°, find the area of the shaded region.​

Answer 1

Answer:

Shaded area = Area of sector OAB - Area of sector OCD

Shaded region = (

360

30

×

7

22

×21×21−

360

30

×

7

22

×7×7)cm

2

Shaded region =

360

30

×

7

22

×(21×21−7×7)cm

2

Shaded area =

42

11

×(21+7)×(21−7)cm

2

Shaded region =

42

11

×28×14 cm

2

= 102.67 cm