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

It is currently 23 Oct 2014, 06:01

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

m20 q32

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 10 Jun 2010
Posts: 10
Followers: 0

Kudos [?]: 1 [0], given: 4

m20 q32 [#permalink] New post 04 Jul 2010, 04:47
A pool can be filled in 4 hours and drained in 5 hours. The valve that fills the pool was opened at 1:00 pm and some time later the drain that empties the pool was also opened. If the pool was filled by 11:00 pm and not earlier, when was the drain opened?

a. at 2:00 pm
b. at 2:30 pm
c. at 3:00 pm
d. at 3:30 pm
e. at 4:00 pm

[Reveal] Spoiler:
When only the valve is open, the pool is filling at a rate of \frac{1}{4} an hour. When both the valve and the drain are open, the pool is filling at a rate of \frac{1}{4} - \frac{1}{5}= \frac{1}{20} an hour. Let x denote the time when only the valve was open. Then both the valve and the drain were open for 11-1-x = 10-x hours. Now we can compose the equation \frac{1}{4}x+\frac{1}{20}(10-x)=1 which reduces to \frac{x}{5}=0.5 from where x=2.5 . Thus, the drain was opened at 1:00 + 2:30 = 3:30 pm.

The correct answer is D.


Can someone please explain/ simplify the wording of the problem for me please?
The explanation provided is straightforward enough, but I could not set the correct equation up because I could get my head round the 3rd statement :oops:
Does the pool fill at 11pm the following day, or was it full at 11pm the previous day?
To derive the solution, does it even matter if the pool was full the previous day or the it filled up the following day?
Manager
Manager
avatar
Joined: 16 Apr 2010
Posts: 223
Followers: 3

Kudos [?]: 46 [0], given: 12

Re: m20 q32 [#permalink] New post 04 Jul 2010, 13:14
Hi,

You have to assume that the pool was empty. Otherwise you cannot solve the problem.

The valve that fills the pool was opened at 1:00 pm in the afternoon just at my lunch time :).

If the pool was filled by 11:00 pm and not earlier, when was the drain opened? Here 11:00pm is 10 hours after my lunch time :) and ie 1 hour just before midnight.

I hope I got your questions right and answered them accordingly.

regards,
Jack
Intern
Intern
avatar
Joined: 10 Jun 2010
Posts: 10
Followers: 0

Kudos [?]: 1 [0], given: 4

Re: m20 q32 [#permalink] New post 04 Jul 2010, 20:50
suddenly it all makes sense
thanks a lot jakolik!
Re: m20 q32   [#permalink] 04 Jul 2010, 20:50
    Similar topics Author Replies Last post
Similar
Topics:
Experts publish their posts in the topic M13 Q 32 teal 2 23 Jan 2012, 20:09
1 m03 Q 32 subhashghosh 1 02 Apr 2011, 18:35
1 Experts publish their posts in the topic m09 Q32 zisis 3 19 Nov 2010, 09:20
8 M14, Q32 : quadrilateral sanjay_gmat 23 18 Mar 2009, 14:12
10 Experts publish their posts in the topic M12 Q32 echizen 20 07 Dec 2008, 09:32
Display posts from previous: Sort by

m20 q32

  Question banks Downloads My Bookmarks Reviews Important topics  

Moderators: WoundedTiger, Bunuel



GMAT Club MBA Forum Home| About| Privacy Policy| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

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®.