Question

The diameter of the base of a right circular cone is 21 cm and its height is 14 cm. Find
curved surface area is :-
(a) 1060 cm
(b) 508 cm
(c) 924 cm
(d) 624 cm​

Answer 1

Answer:

$total curved surface area = 924cm$

Step-by-step explanation:

diameter is 21 cm

diameter $=$ $\frac{radius}{2}$

so,radius will be 10·5 cm

height is 14 cm

$formula for total curved surface area = \pi r(l+r)$

$\pi$ $=$ 3·14

r $=$ radius

l $=$ slant height

$formula for slant height (l) =$$\sqrt{ (10.5)^{2} +(14)^{2} }$

$l = \sqrt{(110.25) + (196) }$

$l = \sqrt{306.25}$

$l = 17.5 cm$

so, total curved surface area will be

$\pi r(l+r) = 3.14*10.5*(17.5+10.5)$

$= 3.14*10.5*28 cm$

$total curved surafe area 924cm$

Answer 2

Curved surface area is 577 cm².

Step-by-step explanation:

In this question we have to calculate the curved surface area which is represented by the formula

S = πrl

which is different from total surface area of the cone represented by the formula :

Total surface area = πr²+πrl

The diameter of the base of right circular cone = 21 cm

Height of the cone = 14 cm

First we calculate the slant height of the cone by the formula :

$l=\sqrt{r^{2}+h^{2}}$

l = slant height

r = radius =  $\frac{1}{2}\times 21$ = 10.5 cm

and h = height = 14 cm

$=\sqrt{(10.5)^{2}+(14)^{2}}$

$=\sqrt{(110.25)+(196)}$

= $\sqrt{306.25}$

l = 17.5 cm

Curved surface area = πrl

$\frac{22}{7}\times 10.5\times 17.5$

= 3.14 × 10.5 × 17.5

= 576.975 ≈ 577 cm²

Curved surface area is 577 cm².

Learn more to find total surface area of a cone : https://brainly.in/question/7033141