Find all School-related info fast with the new School-Specific MBA Forum

 It is currently 01 Jul 2015, 05:11

### 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

# A right circular cylinder

Author Message
Intern
Joined: 10 Apr 2012
Posts: 30
Location: Venezuela
Concentration: General Management, Finance
GPA: 3.07
Followers: 1

Kudos [?]: 30 [0], given: 5

A right circular cylinder [#permalink]  15 Jul 2012, 11:48
1
This post was
BOOKMARKED
A right circular cylinder of 72 cubic meters is completely filled with water. If water evaporates from the cylinder at a constant rate of two liters per hour per one square meter of surface, how long will it take for 30 liters of water to evaporate?

(1) The height of the cylinder is 2 meters.

(2) The radius of the base of the cylinder is 6π√ meters.
Intern
Joined: 10 Apr 2012
Posts: 30
Location: Venezuela
Concentration: General Management, Finance
GPA: 3.07
Followers: 1

Kudos [?]: 30 [0], given: 5

Re: A right circular cylinder [#permalink]  15 Jul 2012, 11:55
I don't understand the highlighted portion of the explanation.

To find the time needed for 30 liters of water to evaporate we need to find the surface area of the top of the cylinder: area/2 will be the amount of water that evaporates each hour, thus time=30/(area/2).

On the other hand since volume=π(r^2)h=72 then area=π(r^2)=72/h. So, basically all we need is ether the area of the surface or the height of the cylinder.

(1) The height of the cylinder is 2 meters. Sufficient.

(2) The radius of the base of the cylinder is 6/√π meters. From this statement we have that area=π(r^2)=36. Sufficient.
Math Expert
Joined: 02 Sep 2009
Posts: 28223
Followers: 4457

Kudos [?]: 44918 [0], given: 6634

Re: A right circular cylinder [#permalink]  16 Jul 2012, 05:11
Expert's post
santivilla wrote:
I don't understand the highlighted portion of the explanation.

To find the time needed for 30 liters of water to evaporate we need to find the surface area of the top of the cylinder: area/2 will be the amount of water that evaporates each hour, thus time=30/(area/2).

On the other hand since volume=π(r^2)h=72 then area=π(r^2)=72/h. So, basically all we need is ether the area of the surface or the height of the cylinder.

(1) The height of the cylinder is 2 meters. Sufficient.

(2) The radius of the base of the cylinder is 6/√π meters. From this statement we have that area=π(r^2)=36. Sufficient.

It should be: To find the time needed for 30 liters of water to evaporate we need to find the surface area of the top of the cylinder: $$2*area$$ will be the amount of water that evaporates each hour, thus $$time=\frac{30}{2*area}$$.

For example if the surface area of the top is 5m^2, then in one hour 5*2=10 liters of water evaporates hence it'll take 30/10=3 hours 30 liters of water to evaporate.

Complete solution.

A right circular cylinder of 72 cubic meters is completely filled with water. If water evaporates from the cylinder at a constant rate of two liters per hour per one square meter of surface of the top, how long will it take for 30 liters of water to evaporate?

To find the time needed for 30 liters of water to evaporate we need to find the surface area of the top of the cylinder: $$2*area$$ will be the amount of water that evaporates each hour, thus $$time=\frac{30}{2*area}$$.

On the other hand since $$volume=\pi{r^2}h=72$$ then $$area=\pi{r^2}=\frac{72}{h}$$. So, basically all we need is ether the area of the surface or the height of the cylinder.

(1) The height of the cylinder is 2 meters. Sufficient.
(2) The radius of the base of the cylinder is $$\frac{6}{\sqrt{\pi}}$$ meters --> $$area=\pi{r^2}=36$$. Sufficient.

_________________
Intern
Joined: 02 Dec 2013
Posts: 7
Followers: 0

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

Re: A right circular cylinder [#permalink]  06 Dec 2013, 23:54
santivilla wrote:
I don't understand the highlighted portion of the explanation.

To find the time needed for 30 liters of water to evaporate we need to find the surface area of the top of the cylinder: area/2 will be the amount of water that evaporates each hour, thus time=30/(area/2).

On the other hand since volume=π(r^2)h=72 then area=π(r^2)=72/h. So, basically all we need is ether the area of the surface or the height of the cylinder.

(1) The height of the cylinder is 2 meters. Sufficient.

(2) The radius of the base of the cylinder is 6/√π meters. From this statement we have that area=π(r^2)=36. Sufficient.

That was really very good question. I wish I could answer that!!! lol
Re: A right circular cylinder   [#permalink] 06 Dec 2013, 23:54
Similar topics Replies Last post
Similar
Topics:
"greater than" means > or = ????? right? 2 01 Nov 2011, 06:06
PS - Water from one cylinder tank to another (m25#37) 6 06 Oct 2011, 02:38
1 M25 only 17 right 1 16 Mar 2010, 21:57
Display posts from previous: Sort by

# A right circular cylinder

Moderators: Bunuel, WoundedTiger

 Powered by phpBB © phpBB Group and phpBB SEO 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®.