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