Question

Find the total surface area of a cone, if its slant height is 21 m and diameter of its base
is 24 m.
​

Answer 1

Given :

• Slant Height of the Cone is 21 m .
• Diameter of the base is 24 m .

To Find :

• Total Surface Area of Cone .

Solution :

$\longmapsto\tt{Slant\:Height(l)=21\:m}$

$\longmapsto\tt{Radius(r)=\cancel\dfrac{24}{2}=12\:m}$

Using Formula :

$\longmapsto\tt\boxed{T.S.A\:of\:Cone=\pi{r(l+r)}}$

Putting Values :

$\longmapsto\tt{\dfrac{22}{7}\times{12}\times{(21+12)}}$

$\longmapsto\tt{\dfrac{264}{7}\times{33}}$

$\longmapsto\tt{\dfrac{8712}{7}}$

$\longmapsto\tt\bf{1244.5\:{m}^{2}}$

So , The Total Surface Area of Cone is 1244.5 m² ..

_______________________

• C.S.A of Cone = πrl
• T.S.A of Cone = πr(l+r)
• Volume of Cone = 1/3 πr²h

Here :

• l = slant height of cone
• r = radius
• h = height

_______________________

Answer 2

Given:

• Slant height of cone, l = 21 m
• Diameter of cone, d = 24 m
• Radius of cone, r = 24/2 = 12 m

To find:

• Total surface area of the cone.

Solution:

As we know that,

⋆ TSA of cone = πr(r + l)

Putting the values,

➜ 22/7 × 12(12 + 21)

➜ 264/7 × 33

➜ 1244.57 m² (approx)

Thus, TSA of cone is 1244.57 m².

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