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Aptitude - Volume and Surface Area - Discussion

Discussion Forum : Volume and Surface Area - General Questions (Q.No. 1)
Volume and Surface Area
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
15 cm3
16 cm3
20 cm3
Answer: 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 8 of 8.
Kanwar Pal Singh said:   1 decade ago
@Swati.

I think you are solving with value of "pi". Otherwise the calculation shit is so simple.
Swati said:   1 decade ago
Anyone solve this last step of questions?

My answer is not coming 12. I think wrong answer.
Prabhu said:   1 decade ago
If it is rotated along the side with 3cm then how could radius be 3cm?
Khushi said:   1 decade ago
As it is mentioned that the triangle is rotated to the side 3 cm. That's the reason it has become the radius of the so formed cone. It has nothing to do with whether it (3 cm side) is considered the base or the height of the triangle!
Nameera khan said:   1 decade ago
How can we know the height is 4 its not given even it can be 5 also did not understand please explain?
Rohit said:   1 decade ago
The only possible explanation is that it is rotated about, not revolved about.

If 5th rotates it means it runs around a fixed center. It rotates about 3 cm side means the 3 cm side is rotating.
King said:   1 decade ago
The Triangle is rotated about the side 3 so it should be the height and the radius should be 4 and According to volume formula to cone its (1/3)*pi*r*r*h in should be 16*pi.
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