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#1 2006-11-21 04:36:02
- Kiran
- Member
- Registered: 2006-11-15
- Posts: 177
volume
find the volume of a right circular cone with a base radius of 3 meters and a slant height of 5 meters.
V = 1/3 ( area of base) (h)
radius = 3m
diameter = 9m = base
v = 1/3 (9)(5)
v = 1/3 ( 45)
v = 15
correct
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#2 2006-11-21 06:46:12
- mathsyperson
- Moderator
- Registered: 2005-06-22
- Posts: 4,900
Re: volume
There are a few mistakes there. To find the base area, you need to use πr². r=3, so πr² = 9π.
Also, the formula for the volume uses the perpendicular height, not the slant height.
If you know that the slant height is 5 and the base radius is 3, you can work out that the perpendicular height is 4, by Pythagoras.
So now you put all that into the formula and you get (1/3)*9π*4 = 12πm³.
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