Question

The perimeter of a semicircular plate is 108 cm. find its area. 

Answer 1

The perimeter of a semi-circular plate = 108 cm
⇒ πr + 2r = 108                 ...(r is radius of a circle )
⇒ r ( π + 2 ) = 108

⇒ r = ` (108)/( π + 2) = (108)/(22/7 + 2)  = (108 xx 7) / (36) = 21 "cm"`

Now, area of a semi-ccircular pleate = `[πr^2]/2   = [22/7 xx 21 xx 21]/2  = 693 "cm"^2`