the diameter of the base of a right circular cone is 21 cm and its hei

1.	the diameter of the base of a right circular cone is 21 cm and its height is 14cm .its curved surface area is
Answer» ANSWER :- Given : Diameter of the base of right circular cone = 21 cm Height = 14 cm To FIND : The curved SURFACE area of the right circular cone. Solution : $\sf Radius \: of \: the \: right \: circular \: cone \: = \: \dfrac{21}{2} \: cm \: = \: 10.5 \: cm$ Let's find the slant height (l) of the right circular cone first. $\boxed{\sf Slant \: height = \: \sqrt{ {r}^{2} + {h}^{2} }}$ $\sf\longrightarrow \sqrt{ {10.5}^{2} + {14}^{2} }$ $\sf\longrightarrow \sqrt{ 110.25 + 196 }$ $\sf\longrightarrow \sqrt{ 306.25 }$ $\sf\longrightarrow 17.5$ .°. The slant height of the cone = 17.5 cm Now, We know that, $\boxed{\sf Curved \: surface \: area \: of \: cone \: = \: \pi \times r \times l}$ [where r = radius and l = slant height of the cone] $\sf\longrightarrow \dfrac{22}{7} \times 10.5 \times 17.5$ $\sf\longrightarrow \dfrac{22}{7} \times \dfrac{105}{10} \times \dfrac{175}{10}$ $\sf\longrightarrow 577.5$ HENCE, the curved surface area of the right circular cone is 577.50 cm²