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 3 of 8.
Sitara said:
8 years ago
Because we are rotating 3cm side which is base to form a cirlce.
Khushi jain said:
8 years ago
How can 3 be the radius? Please explain.
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.
Lingaswamy said:
8 years ago
2πr=3.
r=3/2π.
h=4.
r=3/2π.
h=4.
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.
Ayo said:
8 years ago
I am not getting it. Please, anyone help me to understand it.
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.
Abhinav said:
8 years ago
See in the question it is mentioned that we are rotating the side of 3cm to form cone that means the axis about which we are going to rotate is perpendicular to the side of 3cm. Hence your radius will be 3cm.
Now, just use the formula for volume of cone = 1/3 * π * r^2 * h= 1/3 *π * 9 * 4 = 12πcm^3.
Now, just use the formula for volume of cone = 1/3 * π * r^2 * h= 1/3 *π * 9 * 4 = 12πcm^3.
Lia US said:
8 years ago
Can anyone please explain me this? I didn't understand.
Sameer said:
8 years ago
I could not understand yer, please help me by explaining it.
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