A tank contains 10,000 gallons of a solution that is 5 : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 22 Jan 2017, 15:30

### 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 tank contains 10,000 gallons of a solution that is 5

Author Message
TAGS:

### Hide Tags

Manager
Joined: 02 Dec 2012
Posts: 178
Followers: 5

Kudos [?]: 2331 [0], given: 0

A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

20 Dec 2012, 05:23
7
This post was
BOOKMARKED
00:00

Difficulty:

15% (low)

Question Stats:

75% (02:13) correct 25% (01:34) wrong based on 831 sessions

### HideShow timer Statistics

A tank contains 10,000 gallons of a solution that is 5 percent sodium chloride by volume. If 2,500 gallons of water evaporate from the tank, the remaining solution will be approximately what percent sodium chloride?

(A) 1.25%
(B) 3.75%
(C) 6.25%
(D) 6.67%
(E) 11.7%
[Reveal] Spoiler: OA
Math Expert
Joined: 02 Sep 2009
Posts: 36601
Followers: 7097

Kudos [?]: 93472 [4] , given: 10563

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

20 Dec 2012, 05:25
4
KUDOS
Expert's post
1
This post was
BOOKMARKED
A tank contains 10,000 gallons of a solution that is 5 percent sodium chloride by volume. If 2,500 gallons of water evaporate from the tank, the remaining solution will be approximately what percent sodium chloride?

(A) 1.25%
(B) 3.75%
(C) 6.25%
(D) 6.67%
(E) 11.7%

"The remaining solution will be approximately what percent sodium chloride?" means: what percent of the remaining solution is sodium chloride. Now, since the remaining solution is 10,000-2,500=7,500 gallons and sodium chloride is 500 gallons (5% of initial solution of 10,000 gallons) then sodium chloride is 500/7,500*100=~6.66% of the remaining solution of 7,500 gallons.

Hope it's clear.
_________________
EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 8323
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 382

Kudos [?]: 2469 [1] , given: 163

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

24 Jan 2015, 10:41
1
KUDOS
Expert's post
Sammyh21,

Have you tried doing the math by hand? There's a pattern in the calculation that shouldn't take you too long to find; by extension, the math probably won't take you as long as you might think.

GMAT assassins aren't born, they're made,
Rich
_________________

# Rich Cohen

Co-Founder & GMAT Assassin

# Special Offer: Save \$75 + GMAT Club Tests

60-point improvement guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Math Expert
Joined: 02 Sep 2009
Posts: 36601
Followers: 7097

Kudos [?]: 93472 [1] , given: 10563

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

01 Jun 2016, 08:04
1
KUDOS
Expert's post
Initial amount of water must be 95% of total quantity (9500 gallons); as it's given that 5% (500 gallons) is sodium chloride. lf 2500 gallons of water evaporates, remaining solution should have 7000 gallons of water and 500 gallons of sodium chloride. Then we should have something like: 500/7000, which is clearly wrong.

Could someone please correct where l'm wrong?

Regards.

The remaining solution will be approximately what percent sodium chloride?

The remaining solution = 7000 gallons of water + 500 gallons of sodium chloride = 7500 gallons.

_________________
Senior Manager
Joined: 22 Nov 2010
Posts: 288
Location: India
GMAT 1: 670 Q49 V33
WE: Consulting (Telecommunications)
Followers: 5

Kudos [?]: 138 [0], given: 75

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

08 Mar 2013, 23:09
1
This post was
BOOKMARKED
A tank contains 10,000 gallons of a solution that is 5 percent sodium chloride by volume. If 2,500 gallons of water evaporate from the tank, the remaining solution will be approximately what percent sodium chloride?

(A) 1.25%
(B) 3.75%
(C) 6.25%
(D) 6.67%
(E) 11.7%

5% of 10,000 = 500.

required %age = 500 * 100/7500 = 6.67%
_________________

YOU CAN, IF YOU THINK YOU CAN

Manager
Joined: 29 Mar 2010
Posts: 141
Location: United States
GMAT 1: 590 Q28 V38
GPA: 2.54
WE: Accounting (Hospitality and Tourism)
Followers: 1

Kudos [?]: 114 [0], given: 16

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

30 Jun 2013, 20:12
I have a question.

Are we supposed to assume none of the sodium chloride was evaporated from the same original 10000 Gallons.

Hence of the 500 Gallons of original Sodium Chloride wouldn't the amount of sodium chloride in the solution also decrease by the same rate as the solution without Sodium Chloride?
_________________

4/28 GMATPrep 42Q 36V 640

Math Expert
Joined: 02 Sep 2009
Posts: 36601
Followers: 7097

Kudos [?]: 93472 [0], given: 10563

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

30 Jun 2013, 21:30
hfbamafan wrote:
I have a question.

Are we supposed to assume none of the sodium chloride was evaporated from the same original 10000 Gallons.

Hence of the 500 Gallons of original Sodium Chloride wouldn't the amount of sodium chloride in the solution also decrease by the same rate as the solution without Sodium Chloride?

We are told that from 10,000 gallons of a solution, evaporated 2,500 gallons of water. So, salt did not evaporate.

If it were the way you suggest (if salt evaporated at the same rate as the water) then the answer would simply be 5%.
_________________
Manager
Joined: 29 Mar 2010
Posts: 141
Location: United States
GMAT 1: 590 Q28 V38
GPA: 2.54
WE: Accounting (Hospitality and Tourism)
Followers: 1

Kudos [?]: 114 [0], given: 16

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

30 Jun 2013, 21:51
Bunuel wrote:
hfbamafan wrote:
I have a question.

Are we supposed to assume none of the sodium chloride was evaporated from the same original 10000 Gallons.

Hence of the 500 Gallons of original Sodium Chloride wouldn't the amount of sodium chloride in the solution also decrease by the same rate as the solution without Sodium Chloride?

We are told that from 10,000 gallons of a solution, evaporated 2,500 gallons of water. So, salt did not evaporate.

If it were the way you suggest (if salt evaporated at the same rate as the water) then the answer would simply be 5%.

Ok, I assumed that the two solutions were mixed in the same container.

Thank you Bunuel
_________________

4/28 GMATPrep 42Q 36V 640

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13504
Followers: 577

Kudos [?]: 163 [0], given: 0

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

01 Jul 2014, 06:23
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.
_________________
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 47

Kudos [?]: 1937 [0], given: 193

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

02 Jul 2014, 01:54
This is a inverse proportional problem.

With the salt quantity remaining constant, if the water decreases, it means the percentage of salt increases.

$$\frac{10000}{7500} * 5$$

$$= \frac{20}{3}$$

= 6.67%

_________________

Kindly press "+1 Kudos" to appreciate

Intern
Joined: 13 Dec 2013
Posts: 40
Schools: Fuqua (I), AGSM '16
GMAT 1: 620 Q42 V33
Followers: 2

Kudos [?]: 17 [0], given: 10

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

22 Jul 2014, 18:34
1
This post was
BOOKMARKED
Bunuel, even though the answer doesn't change, I still don't grasp how WATER = SOLUTION evaporated.

I have 10,000 gallons of both: NaCl and Water.
5% of NaCl = 500 gallons so water HAS to be 9,500 gallons.

It explicitly states that 2,500 gallons of water are evaporated, thus our base reduced should be 9,500 - 2,500 = 7,000 gallons of water.

So: NaCl / (NaCl+Water) = 500/(7000+500) = 1/15 = almost 7%.

As said, the answer doesn't change but the concept behind it does.

I don´t know if the problem stem were to change a bit, maybe my explanation might help.
Math Expert
Joined: 02 Sep 2009
Posts: 36601
Followers: 7097

Kudos [?]: 93472 [0], given: 10563

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

23 Jul 2014, 01:32
Enael wrote:
Bunuel, even though the answer doesn't change, I still don't grasp how WATER = SOLUTION evaporated.

I have 10,000 gallons of both: NaCl and Water.
5% of NaCl = 500 gallons so water HAS to be 9,500 gallons.

It explicitly states that 2,500 gallons of water are evaporated, thus our base reduced should be 9,500 - 2,500 = 7,000 gallons of water.

So: NaCl / (NaCl+Water) = 500/(7000+500) = 1/15 = almost 7%.

As said, the answer doesn't change but the concept behind it does.

I don´t know if the problem stem were to change a bit, maybe my explanation might help.

What contradiction do you see between you solution and mine?
_________________
Intern
Joined: 13 Dec 2013
Posts: 40
Schools: Fuqua (I), AGSM '16
GMAT 1: 620 Q42 V33
Followers: 2

Kudos [?]: 17 [0], given: 10

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

23 Jul 2014, 08:27
Bunuel wrote:
Enael wrote:
Bunuel, even though the answer doesn't change, I still don't grasp how WATER = SOLUTION evaporated.

I have 10,000 gallons of both: NaCl and Water.
5% of NaCl = 500 gallons so water HAS to be 9,500 gallons.

It explicitly states that 2,500 gallons of water are evaporated, thus our base reduced should be 9,500 - 2,500 = 7,000 gallons of water.

So: NaCl / (NaCl+Water) = 500/(7000+500) = 1/15 = almost 7%.

As said, the answer doesn't change but the concept behind it does.

I don´t know if the problem stem were to change a bit, maybe my explanation might help.

What contradiction do you see between you solution and mine?

Just read it again, and indeed it is the same. The difference is that I separate both components first, and then subtract 2,500 from Water. You do it the other way around. It should work both ways.

As a chemical engineer, it's difficult not to follow the methodology learned over the years
Current Student
Joined: 09 Dec 2014
Posts: 4
GMAT 1: 710 Q49 V38
Followers: 0

Kudos [?]: 1 [0], given: 13

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

24 Jan 2015, 08:24
How do you convert 1/15 to decimals quickly during the test?

Posted from GMAT ToolKit
Manager
Joined: 16 Jan 2013
Posts: 86
GMAT 1: Q V
GPA: 2.75
Followers: 2

Kudos [?]: 0 [0], given: 746

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

01 Jun 2016, 07:21
Initial amount of water must be 95% of total quantity (9500 gallons); as it's given that 5% (500 gallons) is sodium chloride. lf 2500 gallons of water evaporates, remaining solution should have 7000 gallons of water and 500 gallons of sodium chloride. Then we should have something like: 500/7000, which is clearly wrong.

Could someone please correct where l'm wrong?

Regards.
_________________

Math Forum Moderator
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 2306
Location: India
GPA: 3.5
Followers: 94

Kudos [?]: 637 [0], given: 317

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

01 Jun 2016, 10:45
Initial amount of water must be 95% of total quantity (9500 gallons); as it's given that 5% (500 gallons) is sodium chloride. lf 2500 gallons of water evaporates, remaining solution should have 7000 gallons of water and 500 gallons of sodium chloride. Then we should have something like: 500/7000, which is clearly wrong.

Could someone please correct where l'm wrong?

Regards.

Hope this helps -

Attachment:

Capture.PNG [ 3.75 KiB | Viewed 1658 times ]

Thus the required percentage = $$\frac{500}{7500}$$x$$100$$ => 6.67%
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Senior Manager
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 464
Followers: 22

Kudos [?]: 193 [0], given: 2

Re: A tank contains 10,000 gallons of a solution that is 5 [#permalink]

### Show Tags

23 Jun 2016, 08:39
A tank contains 10,000 gallons of a solution that is 5 percent sodium chloride by volume. If 2,500 gallons of water evaporate from the tank, the remaining solution will be approximately what percent sodium chloride?

(A) 1.25%
(B) 3.75%
(C) 6.25%
(D) 6.67%
(E) 11.7%

We start with 10,000 gallons of a solution that is 5% sodium chloride by volume. This means that there are 0.05 x 10,000 = 500 gallons of sodium chloride.

When 2,500 gallons of water evaporate we are left with 7,500 gallons of solution. From here we can determine what percent of the 7,500 gallon solution is sodium chloride.

(sodium chloride/total solution) x 100 = ?

(500/7,500) x 100 = ?

5/75 x 100 = ?

1/15 x 100 = ?

100/15 = 20/3 = 6 2/3 = 6.67%

_________________

Jeffrey Miller
Jeffrey Miller

Re: A tank contains 10,000 gallons of a solution that is 5   [#permalink] 23 Jun 2016, 08:39
Similar topics Replies Last post
Similar
Topics:
A tank contains 3 13 Feb 2011, 02:03
7 A solution is 90% glycerin. If there are 4 gallons of the solution, ho 9 02 Oct 2010, 05:46
64 Tanks X and Y contain 500 and 200 gallons of water respectiv 30 26 Sep 2010, 19:04
If Henry were to add 5 gallons of water to a tank that is 2 05 Nov 2008, 15:26
24 A tank holds x gallons of a saltwater solution that is 20% 13 22 Feb 2008, 15:33
Display posts from previous: Sort by