It is currently 23 Nov 2017, 06:25

### GMAT Club Daily Prep

#### Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized
for You

we will pick new questions that match your level based on your Timer History

Track

every week, we’ll send you an estimated GMAT score based on your performance

Practice
Pays

we will pick new questions that match your level based on your Timer History

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# The volume of a cylinder is pi * r^2 * h, where r is its

Author Message
Manager
Joined: 20 Mar 2005
Posts: 201

Kudos [?]: 16 [0], given: 0

Location: Colombia, South America
The volume of a cylinder is pi * r^2 * h, where r is its [#permalink]

### Show Tags

13 Nov 2005, 18:31
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

The volume of a cylinder is pi * r^2 * h, where r is its radius and h is its height.
we have two different cylinders, both cylinders have the same height = 8 cms
but cylinder 1 has a diameter of 4 and cylinder 2 has a diameter of 8.
we melt both cylinders and create a sphere, the volume of the sphere is 4/3*pi*r^3, what is the diameter of the sphere?

[/img]

Kudos [?]: 16 [0], given: 0

Senior Manager
Joined: 02 Oct 2005
Posts: 297

Kudos [?]: 24 [0], given: 0

### Show Tags

13 Nov 2005, 19:02
I believe we should use the surface area instead of the volume. Here is how I approached the problem. Correct me if I am wrong.

Surface area of cylinder = 2 * pi * r^2 + 2 * pi * r * h
Surface area of sphere = 4 * pi * r^2

Surface area of sphere = SA of C1 + SA of C2

4 * pi * r^2 = 136 pi

r^2 = 34

r = sqrt(34)
Diameter = 2 * sqrt(34)

Btw, do we have OA?

Kudos [?]: 24 [0], given: 0

SVP
Joined: 16 Oct 2003
Posts: 1798

Kudos [?]: 173 [0], given: 0

### Show Tags

13 Nov 2005, 20:08
I am getting r^3 = 120
r =~5
d = 10

Kudos [?]: 173 [0], given: 0

Director
Joined: 27 Jun 2005
Posts: 501

Kudos [?]: 176 [0], given: 0

Location: MS

### Show Tags

14 Nov 2005, 10:11
volume of First cy + volume of Second cy = volume of sphere

r^3=120
yup

4<r<5....

so diametere is close to 10

what is OA ...?

Kudos [?]: 176 [0], given: 0

Manager
Joined: 20 Mar 2005
Posts: 201

Kudos [?]: 16 [0], given: 0

Location: Colombia, South America

### Show Tags

14 Nov 2005, 12:36
I made this question up, as I got something similar in the real test, not as hard but similar, I agree with Jonny's answer.

Add both volumes and then find r from the sphere, and then multiply by two to find d

Kudos [?]: 16 [0], given: 0

14 Nov 2005, 12:36
Display posts from previous: Sort by

# The volume of a cylinder is pi * r^2 * h, where r is its

Moderator: chetan2u

 Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.