ok i have a "professional tutor" that i'm paying to help and SHE's confused. this problem was not given with a diagram or anything; it's actually two problems in one. I have no idea how to start or continue this one. A hollow cylinder of iron w/height 32 cm. and internal and external radii 4 cm. and 5 cm. respectively is melted to form a solid sphere. Find the radius of the sphere. A convex polygon has 200 sides. How many different diagonals can be drawn in this figure? I'm new here and I NEED HELP!!!!!!
radius of a hollow cylinder NEED HELP!!!
- Thread starter eliza2013
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eliza2013 said:
I don't think this is "two problems in one"....the one about the number of diagonals in a polygon is certainly NOT related to the first problem.
That said, here are some hints on the first problem.
Hint #1....you have a cylinder (the outer one) with radius 4" and height 32 inches....can you find the volume of that cylinder? Another hint....for a cylinder, Volume = pi*r[sup:2p950uip]2[/sup:2p950uip]*h
Hint #2....you have another cylinder (the inner one) with radius 3" and height 32 inches. Find the volume of this cylinder using the formula in hint #1.
Now...subtract the volume of the inner cylinder from the volume of the outer cylinder...this will give you the volume of the "hollow cylinder" to which you refer.
Finally, when you have the volume of the hollow cylinder, you can find the radius of a sphere with that same volume.
Volume of sphere = (4/3)*pi*r[sup:2p950uip]3[/sup:2p950uip]
You know that the volume of the sphere is supposed to be the same as the volume of the hollow cylinder (which you should have found). Substitute that number for the volume of the sphere, and solve for "r".
On the "diagonals of a polygon" problem, you can find many websites which should help you...here's just one of them:
http://www.mathopenref.com/polygondiagonal.html
