Write the area of circle of radius r .

Given: Radius of circle = r We know that, Area of circle = π × r a d i u s 2 Hence, The area of circle of radius r is π r 2

Find the area of shaded region.If A B C D is a square of side 14 c m and A P D and B P C are semicircles.

Given figure is Radius of circle = 7 c m (From the figure) Area of each semicircle = 1 2 π r 2 Area of semicircle A P D = Area of semicircle B P C = 1 2 × 22 7 × 7 2 = 77 c m 2 Area of square A B C D = s i d e 2 = 14 2 = 196 c m 2 Area of shaded region = Area of square A B C D - ( area of semicircle A P D + area of semicircle B P C ) = 196 - 77 + 77 = 196 - 154 = 42 c m 2

Write the perimeter of semicircle of radius r .

Given that, Radius of semicircle is r We know that, The perimeter of a semicircle is the sum of the half of the circumference of the circle and diameter. Circumference of the circle = 2 π r Circumference of the semicircle = π r Diameter of circle = 2 r Perimeter of semicircle = π r + 2 r