Question

Find the curved surface area of a cone whose base radius is 5.6cm and the slant height is 9cm.

Answer 1

Hint:In this question use the direct formula for the curved surface area cone which is $C.S.A=\pi rl$. Here r is the radius of base, l is the slant height of the cone and $\pi$ is a constant.

Complete step-by-step answer:

Given data
Base radius (r) of the cone = 5.6 cm
Slant height (l) of the cone = 9 cm, as shown in figure.
As we know that the curved surface area (C.S.A) of the cone is given as $\pi rl$ unit square.
Therefore substitute all the values in the above equation we have,
$\Rightarrow C.S.A=\pi rl={\displaystyle \frac{22}{7}}\left(5.6\right)\left(9\right)\text{ c}{\text{m}}^2$ $\left[\because \pi ={\displaystyle \frac{22}{7}}\right]$.
Now simplify the above equation we have,
$\Rightarrow C.S.A={\displaystyle \frac{22}{7}}\left(5.6\right)\left(9\right)\text{ = 22}\left(0.8\right)\left(9\right)\text{ = 158}\text{.4 c}{\text{m}}^2$
So this is the required surface area of the cone.
So this is the required answer.

Note:The curved surface area is defined as the area of only curved surfaces leaving the circular top and base. Whereas the total surface area is the area of curved surface area along with the bases. This is the main difference between the curved surface area C.S.A and the total surface area T.S.A.