# Aptitude - Volume and Surface Area - Discussion

Discussion Forum : Volume and Surface Area - General Questions (Q.No. 8)

8.

The slant height of a right circular cone is 10 m and its height is 8 m. Find the area of its curved surface.

Answer: Option

Explanation:

*l* = 10 m,

*h* = 8 m.

So, *r* = *l*^{2} - *h*^{2} = (10)^{2} - 8^{2} = 6 m.

Curved surface area = *rl* = ( x 6 x 10) m^{2} = 60 m^{2}.

Discussion:

11 comments Page 1 of 2.
Akhil said:
4 years ago

@Mustafa.

It is a right circular cone. So given details are height 8 cm, slant height 10 cm, we need to find the base length ie the radius, which can be obtained Pythagoras theorem.

It is a right circular cone. So given details are height 8 cm, slant height 10 cm, we need to find the base length ie the radius, which can be obtained Pythagoras theorem.

(1)

Ngawang Chojey said:
6 years ago

@Nikita is right.

You can use the formula of a right triangle to derive the length of base i.e. equal to radius: h^2=a^2+b^2.

Where, h=slant height, a=hight of a right triangle and b=base of a right triangle.

You can use the formula of a right triangle to derive the length of base i.e. equal to radius: h^2=a^2+b^2.

Where, h=slant height, a=hight of a right triangle and b=base of a right triangle.

(1)

Nikita said:
7 years ago

L = 10 m.

H = 8 m.

R = (10 * 10) - (8 * 8).

R = 100 - 64 = 36.

Square root of 36 is 6.

= 6 * 10 = 60m.

H = 8 m.

R = (10 * 10) - (8 * 8).

R = 100 - 64 = 36.

Square root of 36 is 6.

= 6 * 10 = 60m.

Mustafa said:
7 years ago

Yeah, 10-8 should be 2 not 6.

(1)

Justin said:
7 years ago

Answer is A, why you are taking as a full height of 10?

We need a radius only,

I think;

(22/7) x 6 x 5,

(22/7) x 30 => is a correct Answer.

We need a radius only,

I think;

(22/7) x 6 x 5,

(22/7) x 30 => is a correct Answer.

(1)

Gowtham said:
7 years ago

@Sunil.

How 10-8 = 6?

It should be 2.

How 10-8 = 6?

It should be 2.

(1)

Krutarth vaidya said:
8 years ago

C is also correct.

L = 10,

H = 8,

So, r = l2 - h2 = (10)2 - 82 = 6 m.

Area = 60 m^2.

L = 10,

H = 8,

So, r = l2 - h2 = (10)2 - 82 = 6 m.

Area = 60 m^2.

Islam said:
8 years ago

C is correct.

l = 10 m,

h = 8 m.

So, r = l2 - h2 = (10)2 - 82 = 6 m.

Curved surface area = rl = ( x 6 x 10) m2 = 60 m2.

l = 10 m,

h = 8 m.

So, r = l2 - h2 = (10)2 - 82 = 6 m.

Curved surface area = rl = ( x 6 x 10) m2 = 60 m2.

Subhasis said:
8 years ago

I think r should be 6/2 = 3.

What is the right answer?

What is the right answer?

Sunil said:
8 years ago

Curved surface area of cone = rl.

r stands for radius.

l stands for slant height.

r = ?

height = 8 m.

l = 10 m.

First we should find to r (radius). Then we can find curved surface area of cone.

r = l - r.

r = 10-8 = 6 m.

Put value of r in given formula.

rl = 6 m*10 m = 60 m^2.

(C) 60 m^2 correct option.

r stands for radius.

l stands for slant height.

r = ?

height = 8 m.

l = 10 m.

First we should find to r (radius). Then we can find curved surface area of cone.

r = l - r.

r = 10-8 = 6 m.

Put value of r in given formula.

rl = 6 m*10 m = 60 m^2.

(C) 60 m^2 correct option.

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