Bangun 4
Luas = Luas 1/2 lingkaran
L = 1/2 x π×r²
L = 1/2 x 3,14×10×10
L =1/2 x 314 cm² =157 cm²
Keliling = 4 x jari – jari + Keliling setengah lingkaran
K = (4 x 10) + (1/2 2 π r)
K = 40 + (1/2 x 2 x 3,14 x 10)
K = 40 + (1/2 x 62,8)
K = 40 + 31, 4 = 71,4 cm