Question 22

If the perimeter of a semicircle is 108 cm, then find its area (in cmz).

Solution

Let radius of semi circle = $$r$$ cm

=> Perimeter of semi circle = $$\pi r+2r=108$$

=> $$r(\frac{22}{7}+2)=108$$

=> $$r(\frac{22+14}{7})=108$$

=> $$r=108\times\frac{7}{36}=21$$ cm

$$\therefore$$ Area of semi-circle = $$\frac{1}{2} \pi r^2$$

= $$\frac{1}{2}\times\frac{22}{7}\times(21)^2$$

= $$11\times21\times3=693$$ $$cm^2$$

=> Ans - (C)

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