Aptitude - Volume and Surface Area - Discussion
Discussion Forum : Volume and Surface Area - General Questions (Q.No. 1)
1.
A right triangle with sides 3 cm, 4 cm and 5 cm is rotated the side of 3 cm to form a cone. The volume of the cone so formed is:
12
cm3
cm315 cm3
cm316 cm3
cm320 cm3
cm3Answer: Option
Explanation:
Clearly, we have r = 3 cm and h = 4 cm.
 Volume = |
1 | r2h = |
 |
1 | x x 32 x 4 |
 cm3 |
= 12 cm3. |
| 3 | 3 |
Video Explanation: https://youtu.be/Njsid2mVwUY
Discussion:
77 comments Page 6 of 8.
Sangeethaa Theivendran said:
8 years ago
@ALL.
Just imagine how you draw a circle with radius 3cm using compass. Now look at the shape between two legs of compass. It is a right triangle. Now, if the right triangle is rotated a cone is formed. So radius of cone's base= base of triangle and height of both cone and triangle are same.
Just imagine how you draw a circle with radius 3cm using compass. Now look at the shape between two legs of compass. It is a right triangle. Now, if the right triangle is rotated a cone is formed. So radius of cone's base= base of triangle and height of both cone and triangle are same.
Ayo said:
8 years ago
I am not getting it. Please, anyone help me to understand it.
Dikshant said:
8 years ago
Firstly, we are rotating it not folding it ok we can make a cone by rotating base by 360 degree and the second one is we always follow a sequence in maths base, height and hypotenuse.
Lingaswamy said:
8 years ago
2πr=3.
r=3/2π.
h=4.
r=3/2π.
h=4.
Kaushal said:
8 years ago
Rotated about side 3 means,
height = 3,
base radius = 4,
So area 1/3* π * 16 * 3 = 16 π.
height = 3,
base radius = 4,
So area 1/3* π * 16 * 3 = 16 π.
Khushi jain said:
8 years ago
How can 3 be the radius? Please explain.
Sitara said:
8 years ago
Because we are rotating 3cm side which is base to form a cirlce.
Annu said:
8 years ago
I didn't understand this. Please explain me.
Gopi said:
8 years ago
If base radius of a cone is increased by 20% and its slant height is made double then by how much percent will the area of its curved surface be increased?
a) 140% b) 110% c) 120% d) 130%
a) 140% b) 110% c) 120% d) 130%
DEV RAJ said:
8 years ago
Right triangle is rotated on the axis at 90*, the side of 3 cm is rotated along the axis so diameter is 6 and are = 3.
It is given, if we are rotating on the side 3cm it must be base "see the diagram".
It is given, if we are rotating on the side 3cm it must be base "see the diagram".
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