Semicircle application

Question 1: If the circumference of the semicircle is 180cm what will be the area of the semicircle. Solution: Given: P = 180cm To find: area of semicircle To find area we will need radius, since perimeter is given, lets find radius using the perimeter formula To find radius of semi circle P = r(π + 2) Area of semi circle A = = 11 x 5 x 35 Area = 1925 cm (Ans) 11 5 5 30 6 r = 5 x 7 = 35cm

Question 2: Perimeter of semicircle is 324cm. Find its radius. Arc length of semi-circle = r(π + 2) 324 = r(π + 2) 9 54 6 r = 9 x 7 = 63cm (ans)

Question 3: Perimeter of semicircle is 144m. Find its diameter. 144cm Arc length of semi-circle = r(π + 2) 144 = r(π + 2) 4 24 6 r = 4 x 7 = 28m d = 2 x r = 2 x 28 = 56 m (ans)

A B C Question 4: Calculate perimeter of the shape below 12.57cm 4cm Semi-circle of diameter = 8cm A Semi-circle of diameter = 4cm 4cm Semi-circle of diameter = 4cm 4cm 4cm B C 6.29cm 6.29cm Perimeter of combined Shapes= Perimeter of A + Perimeter of B + Perimeter of C Arc length of semi-circle A = Arc length of semi-circle B or C = =12.57cm =6.29cm Perimeter of combined Shapes= 12.57cm + 6.29cm + 6.29cm = 25.15cm

Recap A semicircle is half part of a circle Perimeter of a semicircle = r(π + 2) Area of a semicircle =

Try these Find the perimeter and area of a semi circle whose radius is 21 cm. Find the area of the semicircle whose circumference is 108cm