Answers

2016-03-18T18:24:33+05:30
I guess you mentioned the figure attached herealong

so for this figure, there are 2 semicircles APB and AQO

as AO=OB=r( given)
 
Perimeter of shaded region = circumference of semicircle APB + circumference of semicircle AQO
40 =  \pi r + \pi r/2

80 = 3
  \pi r
r= 80/3
  \pi           ...........1

Now Area of shaded region = 
  \pi r^2 +   \pi (r/2)^2  = (5  \pi r^2)/4

Putting value of r from 1
we get area of shaded region  as  283.09cm^2
1 5 1