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A cone is cut off the up part

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by CrackGMAC » Thu Aug 27, 2009 8:09 am
121. A cone is cut off the up part (The new plane should be parallel to the bottom). The diameter of two circles is given, what is the surface area of the geometric form (not including two bottom?)?
1). Height of the form is ...
2). The circle in the middle plane has a diameter... IMO [spoiler]A[/spoiler]
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Source: — Problem Solving |

by BrianSmith » Sun Aug 30, 2009 4:00 am
I don't understand: is the diameter of top circle given in the question or in the second statement? Or are there three circles (and hence a middle one)?
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by CrackGMAC » Fri Sep 04, 2009 6:22 am
I believe there are three circles
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Re: A cone is cut off the up part

by maihuna » Fri Sep 04, 2009 6:42 am
CrackGMAC wrote:121. A cone is cut off the up part (The new plane should be parallel to the bottom). The diameter of two circles is given, what is the surface area of the geometric form (not including two bottom?)?
1). Height of the form is ...
2). The circle in the middle plane has a diameter... IMO [spoiler]A[/spoiler]
This is about frustum of a cone. You may draw a cone and remove the top, what is being asked is the lateral surface after the removal.

The lateral surface is IIrl here r will be 1/2(r1+r2) and given r and h we may find l, so C should be answer.

what is the source of the Q
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