Surface Areas and Volumes — Question 1

Given,

Diameter of cone (d) = 10.5 cm

Slant height of cone (l) = 10 cm

By formula,

Radius of cone (r) = $\dfrac{\text{Diameter}}{2} = \dfrac{10.5}{2}$ = 5.25 cm

By formula,

Curved surface area of cone (C.S.A.) = πrl

Substituting values we get :

$\text{C.S.A.} = \dfrac{22}{7} × 5.25 × 10 \\[1em] = \dfrac{1155}{7} \\[1em] = 165 \text{ cm}^2$

Hence, curved surface area of the cone = 165 cm².