The surface area of a cone consists of the area of lateral side and the area of the base. The area of lateral side is determined using (π × r × s), s represents the slant height. The area of the base is determined using the formula of the area of a circle.
area of lateral side + area of base = surface area
(π × r × s) + (π × r²) = surface area
Input the numbers
(π × r × s) + (π × r²) = surface area
(π × 10 × s) + (π × 10²) = 150π
10πs + 100π = 150π
10πs = 150π - 100π
10πs = 50π
s = 50π/10π
s = 5
The slant height is 5 inches