Question

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

Answer 1

Answer:

1244.57 m2

Step-by-step explanation:

Now, the total surface area of cone is given by

S=πrl+πr

2

S=π(rl+r

2

)

S=π(12×21+12

2

)

S=π(252+144)

S=

7

22

×396

hence, S=1244.57 m

2

Answer 2

Given:

• Slant Height = 21m
• Diameter of its base = 24m

To Find:

• Total surface area of cone = ?

Solution:

According to the question,slant height of cone is given 21 m and diameter of its base is 24m and said to find total surface area of cone. So firstly, we will find the radius of the cone because as we know that in the formula of total surface area needed radius not diameter.

As we know that,

$\sf{ Radius = (\dfrac{Diameter}{2})}$

$\: \: \sf \rightarrow \: r = \frac{24}{2} \\ \\ \: \: \sf \rightarrow \: r = 12m$

Now,we know that

$\: \: \sf total \: surface \: area = \pi \: rl \: + \pi \: {r}^{2}$

Now put the formula

$\: \: \sf \:t.s.a = \pi \: (rl + {r}^{2} ) \\ \\ \: \: \sf t.s.a = \pi \: (12 \times 21 + {12}^{2}) \\ \\ \: \: \sf \: t.s.a = \pi \: (252 + 144) \\ \\ \: \: \sf \:t.s.a = \frac{22}{7} \times 396 \\ \\ \: \: \sf \:t.s.a = 1244.57 {m}^{2}$

Hence, Total surface area is 1244.57 m^2.

Note:-

• L denotes here Slant height of cone.
• R denotes here radius of cone.