Question

What is the surface area of the right cone below?

Answer 1

Formula for surface area of cone:

`A= \pi r(r+ √(h^2+r^2) )`
Here Radius, r= 6 units
To find the height of cone, we use Pythagorean theorem.
c²=a²+b²
Put values
15²=6²+h²
225=36+h²
h²=189
Put values in formula.
A=6π(6+√189+36)
A=6π+(6+√225)
A=6π(6+15)
A=126π units²

Answer 2

Te correct option B.

Explanation:

The surface area of a cone is

`A=\pi r(r+l)`

Where, r is the radius and l is slant height.

From the given figure it is noticed that the radius of the cone is 6 and slant height is 15.

The surface area of cone is

`A=\pi * 6* (6+15)`

`A=\pi * 6* 21`

`A=126\pi`

The area of the cone is 126π units². Therefore option B is correct.