I know there are solutions to this question posted https://www.beatthegmat.com/cone-is-insc ... 33925.html, however I have a follow-up clarifying question.
A right circular cone is inscribed in a hemisphere so that the base of the cone coincides with the base of the hemisphere. What is the ratio of the height of the cone to the radius of the hemisphere?
Answer is 1:1
My question is, if you have a cone with a radius of 5 and a height of 1, how could the ratio be 1:1? You could have a very wide and short hemisphere. Am I missing something with regards to the cone being designated as a "right circular cone"? Can someone please explain?
Right Circular Cone
This topic has expert replies
-
- Senior | Next Rank: 100 Posts
- Posts: 54
- Joined: Sat May 18, 2013 10:24 am
- Thanked: 1 times
- Followed by:1 members
I believe I just figured it out. One of the properties of a sphere is that it is perfectly symmetrical. As such, the radius will also equal the height. If you have a right cone inscribed inside the hemisphere, the height of the cone will equal the radius of the hemisphere due to the symmetrical properties of spheres and hemispheres.
Is that right?
Is that right?
- GMATGuruNY
- GMAT Instructor
- Posts: 15539
- Joined: Tue May 25, 2010 12:04 pm
- Location: New York, NY
- Thanked: 13060 times
- Followed by:1906 members
- GMAT Score:790
Draw the figure:
As the figure illustrates, the height of the cone = the radius of the hemisphere.
Thus:
(height of cone) : (radius of hemisphere) = 1:1.
As the figure illustrates, the height of the cone = the radius of the hemisphere.
Thus:
(height of cone) : (radius of hemisphere) = 1:1.
Private tutor exclusively for the GMAT and GRE, with over 20 years of experience.
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
Followed here and elsewhere by over 1900 test-takers.
I have worked with students based in the US, Australia, Taiwan, China, Tajikistan, Kuwait, Saudi Arabia -- a long list of countries.
My students have been admitted to HBS, CBS, Tuck, Yale, Stern, Fuqua -- a long list of top programs.
As a tutor, I don't simply teach you how I would approach problems.
I unlock the best way for YOU to solve problems.
For more information, please email me (Mitch Hunt) at [email protected].
Student Review #1
Student Review #2
Student Review #3
I don't know if necroing is allowed on Beat The GMAT, feel free to delete my post and I'll make another one if required.
This explanation isn't sufficient to me. It doesn't address the OP's question: what in the formulation of the question prevents a cone with a base of radius r and a height of h where h≠r? Is it the fact that it is inscribed? If so, what does inscribed actually mean in this context?
This explanation isn't sufficient to me. It doesn't address the OP's question: what in the formulation of the question prevents a cone with a base of radius r and a height of h where h≠r? Is it the fact that it is inscribed? If so, what does inscribed actually mean in this context?
- DavidG@VeritasPrep
- Legendary Member
- Posts: 2663
- Joined: Wed Jan 14, 2015 8:25 am
- Location: Boston, MA
- Thanked: 1153 times
- Followed by:128 members
- GMAT Score:770
You answered your own question Yes, it's the fact that the cone is inscribed that necessitates that h = r. "Inscribed" simply means that one figure is inside of another and that the two figures are touching at as many points as possible.This explanation isn't sufficient to me. It doesn't address the OP's question: what in the formulation of the question prevents a cone with a base of radius r and a height of h where h≠r? Is it the fact that it is inscribed? If so, what does inscribed actually mean in this context?
-
- GMAT Instructor
- Posts: 2630
- Joined: Wed Sep 12, 2012 3:32 pm
- Location: East Bay all the way
- Thanked: 625 times
- Followed by:119 members
- GMAT Score:780
In the 2D world, a polygon inscribed in a circle has each vertex on that circle's circumference, while a circle inscribed in a polygon is tangent to each side of the polygon. (See some images here.)inigohrey wrote:I don't know if necroing is allowed on Beat The GMAT, feel free to delete my post and I'll make another one if required.
This explanation isn't sufficient to me. It doesn't address the OP's question: what in the formulation of the question prevents a cone with a base of radius r and a height of h where h≠r? Is it the fact that it is inscribed? If so, what does inscribed actually mean in this context?
From there, you can probably guess how to generalize this to 3D, 4D, etc.
-
- GMAT Instructor
- Posts: 2630
- Joined: Wed Sep 12, 2012 3:32 pm
- Location: East Bay all the way
- Thanked: 625 times
- Followed by:119 members
- GMAT Score:780
It's definitely allowed, at least in practice - it seems to happen almost every day.inigohrey wrote:I don't know if necroing is allowed on Beat The GMAT, feel free to delete my post and I'll make another one if required.
-
- GMAT Instructor
- Posts: 2630
- Joined: Wed Sep 12, 2012 3:32 pm
- Location: East Bay all the way
- Thanked: 625 times
- Followed by:119 members
- GMAT Score:780
I almost forgot the most salient point (no pun intended): cones are the white whale of the GMAT. I've heard them mentioned and seen them in problems from a few test prep providers, but I've never seen an official problem that required you to know anything specific to cones. (I can't even remember seeing one that involved cones at all, but I'm sure someone here can correct me.)