Question

AB and CD are respectively ares of two concentric circles of radii21 cm and 7 em with centre
O (See figure). If ZAOB = 30°, find the area of the shaded region

Answer 1

Answer:

Step-by-step explanation:

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  

2