GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 19 Nov 2019, 20:40

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.

Close

Request Expert Reply

Confirm Cancel

If Pool Y currently contains more water than Pool X, and if

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

Find Similar Topics 
Intern
Intern
avatar
Joined: 09 Nov 2010
Posts: 9
DS: Pool Y and Pool X  [#permalink]

Show Tags

New post 07 Dec 2010, 08:21
5
18
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

69% (01:46) correct 31% (01:53) wrong based on 447 sessions

HideShow timer Statistics

If Pool Y currently contains more water than Pool X, and if Pool X is currently filled to 2/7 of its capacity, what percent of the water currently in Pool Y needs to be transferred to Pool X if Pool X and Pool Y are to have equal volumes of water?

(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity.

(2) Pool X has a capacity of 14,000 gallons.

Spoiler: :: Doubt
Hi.

I came across this DS question on my last MgCAT, and while I do understand how to solve it, I fail to see why (according to the Mg explanation) we should consider both pools capacity as equal, when nothing in the text leads to that assumption… (or am I missing something here?)

Therefore I felt for E.

Thanks for the help.
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59147
Re: Can someone clear out this DS question for me plz.  [#permalink]

Show Tags

New post 07 Dec 2010, 09:10
16
5
itnas wrote:
Hi.

I came across this DS question on my last MgCAT, and while I do understand how to solve it, I fail to see why (according to the Mg explanation) we should consider both pools capacity as equal, when nothing in the text leads to that assumption… (or am I missing something here?)

Therefore I felt for E.

Thanks for the help.


If Pool Y currently contains more water than Pool X, and if Pool X is currently filled to 2/7 of its capacity, what percent of the water currently in Pool Y needs to be transferred to Pool X if Pool X and Pool Y are to have equal volumes of water?

(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity.

(2) Pool X has a capacity of 14,000 gallons.


We are nowhere told that the capacities of pools X and Y are equal.

(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity --> together pools X and Y contain 6/7 of the capacity of pool X. Now, in order pools X and Y to contain equal amount of water each pool should contain 3/7 of the capacity of pool X, thus from pool Y, which contains 4/7 (6/7-2/7=4/7) of the capacity of pool X we must transfer 1/7 of the capacity of pool X, which is 25% of the water currently in pool Y (1/7)/(4/7)=1/4. Sufficient.

Or consider the following:
Let the capacity of pool X be 7 gallons. It's 2/7 full, thus there are 2 gallons of water. If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity and thus will contain 6 gallons of water, which means that there are now 6-2=4 liters of water in pool Y (it doesn't matter what capacity it has). In order both pools to contain equal amount of water each pool should contain 3 gallons of water, thus we should transfer 1 gallon from pool Y to pool X. 1 gallon is 1/4 of the water currently in pool Y.

(2) Pool X has a capacity of 14,000 gallons. No info about pool Y. Not sufficient.

Answer: A.

Hope it's clear.
_________________
General Discussion
Intern
Intern
avatar
Joined: 09 Nov 2010
Posts: 9
Re: Can someone clear out this DS question for me plz.  [#permalink]

Show Tags

New post 07 Dec 2010, 09:22
2
Thanks, I guess I just got blinded by not knowing the capacity of either pools.

Your explanations just remind me the scene of Die Hard 3 when transferring gallons of water from one “jar” to another in order to disarm the bomb :lol:
Intern
Intern
avatar
Joined: 06 Dec 2010
Posts: 15
Re: Can someone clear out this DS question for me plz.  [#permalink]

Show Tags

New post 07 Dec 2010, 20:36
1
Haha! I started reading the question and thought of the same thing... ahhhh the 90s action movies
Director
Director
avatar
Joined: 01 Feb 2011
Posts: 533
Re: Pool Capacity  [#permalink]

Show Tags

New post 18 Sep 2011, 15:55
1
Lets say pool x's total capacity = x
=> Pool x filled capacity = (2/7)x

Lets say pool y's total capacity = y

lets say pool y's filled capacity = py ( where p is some fraction)

Let r be the volume transferred from y to x.

if py - r = (2/7)x+r , r is what percent of py?

1. Sufficient

py- r = (2/7)x+r = (6/7)x

(2/7)x+r = (6/7)x => r = (4/7)x

py - r = (6/7)x => py = (10/7)x

r is what percent of py? i.e is (((4/7)x) / ((10/7)x)) *100

= (4/10)*100

2. Not sufficient
we dont know anything about pool y or how much removed from pool y.

Answer is A.
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59147
Re: If Pool Y currently contains more water than Pool X, and if  [#permalink]

Show Tags

New post 24 Jun 2013, 03:17
Intern
Intern
avatar
Joined: 22 May 2013
Posts: 43
Concentration: General Management, Technology
GPA: 3.9
WE: Information Technology (Computer Software)
GMAT ToolKit User
Re: If Pool Y currently contains more water than Pool X, and if  [#permalink]

Show Tags

New post 24 Jun 2013, 11:33
1
Bunuel wrote:
Bumping for review and further discussion*. Get a kudos point for an alternative solution!

*New project from GMAT Club!!! Check HERE

All DS Fractions/Ratios/Decimals questions: search.php?search_id=tag&tag_id=36
All PS Fractions/Ratios/Decimals questions: search.php?search_id=tag&tag_id=57


Question:
Let the capacity of X be C
so, X= 2C/7 and Y>X
If n is the quantity of water taken from Y and put into X
Then,
Y-n = X+n
2n = Y-X => n = (Y-X)/2
n is the quantity that needs to be transferred.
The % will (n/Y) * 100 %
(Note, that we already have one equation with X and C, and we just need one more involving Y and C, if we can get it out of any of the statements, it should be enough to solve)
Now lets take a look at the statements :

(1) If all the water currently in Pool Y were transferred to Pool X, Pool X would be filled to 6/7 of its capacity.

Y+X = 6C/7
and we know that X=2C/7

Hence, Y=4C/7

n = (Y-X)/2 = C/7
Therefore, % of water = (C/7)/(4C/7) *100
=100/4
=25%

Sufficient.

(2) Pool X has a capacity of 14,000 gallons.

We need another relation in Y and C or Y and X to be able to solve, not sufficient.

Ans: A
_________________
PS: Like my approach? Please Help me with some Kudos. :-)
Manager
Manager
User avatar
B
Joined: 07 Jun 2018
Posts: 104
If Pool Y currently contains more water than Pool X, and if  [#permalink]

Show Tags

New post 15 Jun 2018, 13:12
I just keep cheating! I look at the answers before selecting an answer.
Am I spoiling something?
The statistics I guess!

Posted from my mobile device
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 59147
Re: If Pool Y currently contains more water than Pool X, and if  [#permalink]

Show Tags

New post 15 Jun 2018, 22:52
1
Manager
Manager
User avatar
B
Joined: 07 Jun 2018
Posts: 104
Re: If Pool Y currently contains more water than Pool X, and if  [#permalink]

Show Tags

New post 16 Jun 2018, 02:53
Bunuel wrote:
MrJglass wrote:
I just keep cheating! I look at the answers before selecting an answer.
Am I spoiling something?
The statistics I guess!

Posted from my mobile device


Checking the Spoiler OA does not affect stats. Though if you click A, B, C, D E, buttons in timer just to see the OA, that does.


Okay, thanks for the info.
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 13610
Re: If Pool Y currently contains more water than Pool X, and if  [#permalink]

Show Tags

New post 14 Jul 2019, 09:45
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
GMAT Club Bot
Re: If Pool Y currently contains more water than Pool X, and if   [#permalink] 14 Jul 2019, 09:45
Display posts from previous: Sort by

If Pool Y currently contains more water than Pool X, and if

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne