Two concentric circles of radii 21cm and 42cm angle aob is 60
Answers
Radii of the concentric circles = 21 cm and 42 cm Area between the circles = π R2 - r2 = (22/7) (422 - 212) = 4158 cm2 Angle subtended by the arc in the inner circle = 60° Area of the sector in the inner circle = (60° / 360°) x π r2 = (60° / 360°) x (22/7) x (21)2 = 231 cm2 Angle subtended by the arc in the outer circle = 60° Area of the sector in the inner circle = (60° / 360°) x π R2 = (60° / 360°) x (22/7) x (42)2 = 924 cm2 Area of the portion of the sector in between the circles = 924 - 231 = 693 cm2 Area of the shaded portion = (Area between the circles) - (Area of the portion of the sector in between the circles) = 4158 - 693 = 3465 Therefore, the area of the shaded region is 3465 cm2.