What is the surface are of a right circular cone if the cone's diameter is 10cm and the lenght is 20cm.

Question

HElp please.

Answer 1

The diameter (d ) of right circular cone is 10 cm and its length (h ) is 20 cm.

Lateral Surface Area of right circular cone : A = πrs = πr * sqrt (r² + h²),

where r = radius of the base (circle) = d/2 = 10/2 = 5 cm.

          h = height of the cone = 20 cm.

          s = slant height = sqrt (r² + h²) = sqrt (5² + 20²) =  sqrt (25+ 400) =  sqrt (425) =  √425 cm

  and  π = 3.14.

Lateral Surface Area of right circular cone : A = πrs = 3.14 * 5 * √425 = 3.14 * 5 * 20.61 = 323.66 cm²

Total Surface Area of right circular cone : A = πr² + πrs.

A = (3.14 * 5²) + (3.14 * 5 * √425)

A = (3.14 * 25) + (3.14 * 5 * 20.61).

A = 78.5 + 324.6075

A = 403.1075 cm².

Lateral surface area of right circular cone is 323.66 cm² and its total surface area is 403.1075 cm².