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.
Vikash said:
9 years ago
According to me, the language of the question is wrong. Because if it is rotated by side 3cm, its radius will never be 3cm, if anybody visualizes it?
Shivang said:
9 years ago
The question is incomplete, it is not mentioned that the 3 cm is the base. And if it is then cone thus formed has symmetry about x-axis with height 3cm.
Sateesh kumar Routhu said:
9 years ago
Hello friends,
3, 4, 5 are the sides and hypotenus of the right angle triangle, i.e. root of 3^2 + 4^2 = 5, in this we can take either 3, 4 or 4, 3 as sides and 5 as a hypotenus. Then we take radious and height of the cone are r = 3, h = 4, or r = 4, h = 3.
We are able to form two cones of different sizes with same area and volume. i.e volume is 12 pi cm^3.
3, 4, 5 are the sides and hypotenus of the right angle triangle, i.e. root of 3^2 + 4^2 = 5, in this we can take either 3, 4 or 4, 3 as sides and 5 as a hypotenus. Then we take radious and height of the cone are r = 3, h = 4, or r = 4, h = 3.
We are able to form two cones of different sizes with same area and volume. i.e volume is 12 pi cm^3.
Anil sarode said:
9 years ago
You are absolutely right @Rohit.
Archana said:
9 years ago
How you take 3cm for the base?
Please, Explain.
Please, Explain.
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.
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