Question

The radius of a cone is 3 cm and the surface area is 81pi cm squared. Find the slant height of this cone.

Answer 1

24cm

1) We can find out the slant height of that cone by making use of the following:

`\begin{gathered} R=3 \\ A=\pi r\mleft(s+r\mright) \\ \end{gathered}`

2) Plugging into that we can write out:

`\begin{gathered} 81\pi=3\pi(s+3) \\ (81\pi)/(3\pi)=(3\pi(s+3))/(3\pi) \\ 27=s+3 \\ 27-3=s \\ s=24 \end{gathered}`

Hence, the slant height is 24 cm