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Maths Exercices

Surface area of cones

A cone is a solid pointed figure with a circular base. A cone is a kind of pyramid whose base is a circle.

To find the total surface area of a cone, first find the area of the base and then find the lateral surface area. The total surface area of the cone includes the area of the base and the area of the lateral surface area. That is:


What is the surface area of this cone? Use π ≈ 3.14

Find the radius and slant height of the cone.

radius = 4

slant height = 6


Find the area of the base. Use π ≈ 3.14.

Area of base
=
π
r
2

≈
3.14 ×
4 2

≈ 50.24


Find the lateral area.

Lateral area
=
π
r
l

≈
3.14 ×
4 × 6

≈ 75.36


Now add the areas to find the surface area of the cone.

Surface area
=
area of base
+
lateral area

≈
50.24 + 75.36

≈ 125.6


The surface area of the cone is about 125.6 square centimeters.

What is the surface area of this cone when r=8 and l=4


Use =3.14