Formula of the surface area of a cone is:
S.A = Area of base + [tex] \frac{1}{2} [/tex] × Perimeter of base × height of prism
S.A = [tex] \pi [/tex]r² + [tex] \pi [/tex]rl
= [tex] \pi [/tex](7)² + [tex] \pi [/tex](7)(18)
= 49[tex] \pi [/tex] + 126[tex] \pi [/tex]
= 175[tex] \pi [/tex] in² (in terms of [tex] \pi [/tex])
= 549.7787 in²
≈ 550 in²
