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

It is currently 25 Oct 2014, 01:37

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

A 20 litre mixture of milk and water contains milk and water

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
2 KUDOS received
Current Student
User avatar
Joined: 29 Jan 2005
Posts: 5252
Followers: 23

Kudos [?]: 140 [2] , given: 0

Reviews Badge
A 20 litre mixture of milk and water contains milk and water [#permalink] New post 29 Oct 2005, 09:32
2
This post received
KUDOS
3
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

80% (02:26) correct 20% (01:57) wrong based on 172 sessions
A 20 litre mixture of milk and water contains milk and water in the ratio 3 : 2. 10 litres of the mixture is removed and replaced with pure milk and the operation is repeated once more. At the end of the two removal and replacement, what is the ratio of milk and water in the resultant mixture?

A. 17 : 3
B. 9 : 1
C. 3 : 17
D. 5 : 3
E. 11: 2
[Reveal] Spoiler: OA

Last edited by Bunuel on 01 Jun 2012, 00:39, edited 1 time in total.
Edited the question and added the OA
Expert Post
8 KUDOS received
Veritas Prep GMAT Instructor
User avatar
Joined: 16 Oct 2010
Posts: 4877
Location: Pune, India
Followers: 1157

Kudos [?]: 5381 [8] , given: 165

Re: A 20 litre mixture of milk and water contains milk and water [#permalink] New post 26 Apr 2012, 05:29
8
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
GMATT73 wrote:
A 20 litre mixture of milk and water contains milk and water in the ratio 3 : 2. 10 litres of the mixture is removed and replaced with pure milk and the operation is repeated once more. At the end of the two removal and replacement, what is the ratio of milk and water in the resultant mixture?

(1) 17 : 3
(2) 9 : 1
(3) 3 : 17
(4) 5 : 3
(5) 11: 2


Use this:

New Concentration of Water = Old concentration of Water * (V1/V2)^n

New Concentration of Water = 2/5 * (1/2)^2 = 1/10

Ratio of milk:water = 9:1

Complete explanation of this formula and method is given here: http://www.veritasprep.com/blog/2012/01 ... -mixtures/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Save $100 on Veritas Prep GMAT Courses And Admissions Consulting
Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options.

Veritas Prep Reviews

2 KUDOS received
Manager
Manager
avatar
Joined: 01 Aug 2005
Posts: 68
Followers: 1

Kudos [?]: 3 [2] , given: 0

 [#permalink] New post 29 Oct 2005, 09:51
2
This post received
KUDOS
2) 9 : 1

From the beginning;
Initially milk to water is 12l : 8l
remove half 6 - 4
add 10l milk 16 - 4
remove half 8 - 2
add 10l milk 18 - 2
18:2 = 9:1
2 KUDOS received
Intern
Intern
avatar
Joined: 26 Apr 2012
Posts: 5
Followers: 0

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

Re: A 20 litre mixture of milk and water contains milk and water [#permalink] New post 26 Apr 2012, 02:41
2
This post received
KUDOS
he 20 litre mixture contains milk and water in the ratio of 3 : 2. Therefore, there will be 12 litres of milk in the mixture and 8 litres of water in the mixture.

Step 1.
When 10 litres of the mixture is removed, 6 litres of milk is removed and 4 litres of water is removed. Therefore, there will be 6 litres of milk and 4 litres of water left in the container. It is then replaced with pure milk of 10 litres. Now the container will have 16 litres of milk and 4 litres of water.

Step 2.
When 10 litres of the new mixture is removed, 8 litres of milk and 2 litres of water is removed. The container will have 8 litres of milk and 2 litres of water in it. Now 10 litres of pure milk is added. Therefore, the container will have 18 litres of milk and 2 litres of water in it at the end of the second step. Therefore, the ratio of milk and water is 18 : 2 or 9 : 1.

Shortcut.
We are essentially replacing water in the mixture with pure milk.
Let W_o be the amount of water in the mixture originally = 8 litres.
Let W_r be the amount of water in the mixture after the replacements have taken place.
Then,{W_r}/{W_o}= (1-R/M)^n
where R is the amount of the mixture replaced by milk in each of the steps, M is the total volume of the mixture and n is the number of times the cycle is repeated.

Hence, {W_r}/{W_o} =(1/2)^2  =1/4
Therefore, "W_r ={W_o}/4= 8/4 = 2 litres

Reference: lofoya. com/Aptitude-Questions-And-Answers/Alligation-or-Mixture/l3p1 .htm

Hope it helps :)
2 KUDOS received
Manager
Manager
User avatar
Joined: 28 Jul 2011
Posts: 213
Followers: 0

Kudos [?]: 34 [2] , given: 13

Re: A 20 litre mixture of milk and water contains milk and water [#permalink] New post 31 May 2012, 19:23
2
This post received
KUDOS
I just learned the new method to solve this problem as discussed by Karishma from veritas link, Trying to solve this question using that method

For future reference

total solution : 20 liters
milk : water 3:2

milk = 12 liters
water = 8 liters

Amount = Concentratio * volumn
therefore concentration of water in the solution is

8 = Cw * 20
Cw = 2/5

Step 1: 10 liters from 20 liters solution is removed - in the leftover solution the concentration of water remains the same. i.e. 2/5. Intial volume of solution was 20, new volumn is 10 (after 10 liter is removed)

Step 2: 10 liters of pure milk is added to the solution, therefore new solution is again 20 liters

Initial COncentration (Ci) * Initial Volumn (Vi) = Final Contentration (Cf) * final Volumn (Vf)
(2/5) * 10 = Cf * 20
Cf = 2/5 (1/2) (the amount of water will remain the same when as initial in (10 liter solution) but concentration of water will changes when milk is added to intial 10 liter water)


Step 3 now again from the Step 2 solution we remove 10 liter solution and added 10 liter pure milk

cf = (2/5) (1/2) (1/2)
cf = 1/10 (this is a new concentration of Water in the solution)

there fore concentration of milk is 9/10

therefore ratio of milk : water is 9:1
VP
VP
avatar
Joined: 30 Sep 2004
Posts: 1493
Location: Germany
Followers: 4

Kudos [?]: 52 [0], given: 0

 [#permalink] New post 29 Oct 2005, 09:48
x/8=(1-10/20)^2 => x=amount of water left after 2 removements. its 9:1...
_________________

If your mind can conceive it and your heart can believe it, have faith that you can achieve it.

Manager
Manager
avatar
Joined: 01 Aug 2005
Posts: 68
Followers: 1

Kudos [?]: 3 [0], given: 0

 [#permalink] New post 29 Oct 2005, 09:52
Chris I dont really understand your reasoning, care to explain a bit where the numbers come from. Thanks.
VP
VP
avatar
Joined: 30 Sep 2004
Posts: 1493
Location: Germany
Followers: 4

Kudos [?]: 52 [0], given: 0

 [#permalink] New post 29 Oct 2005, 10:27
xennie wrote:
Chris I dont really understand your reasoning, care to explain a bit where the numbers come from. Thanks.


usually i use this formula for these kind of questions...
amount of x after removal/total amount of x=(1-(amount of y that is replaced)/total volume)^number of replacements...not the best but the fastest way unless its trickier...
_________________

If your mind can conceive it and your heart can believe it, have faith that you can achieve it.

Manager
Manager
avatar
Joined: 01 Aug 2005
Posts: 68
Followers: 1

Kudos [?]: 3 [0], given: 0

 [#permalink] New post 29 Oct 2005, 10:31
Where did you get it from? Might be useful to memorize a few of those formulas for the actual exam.
CEO
CEO
User avatar
Joined: 09 Sep 2013
Posts: 2865
Followers: 207

Kudos [?]: 43 [0], given: 0

Premium Member
Re: A 20 litre mixture of milk and water contains milk and water [#permalink] New post 30 Sep 2013, 13:43
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 Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Manager
Manager
avatar
Joined: 23 May 2013
Posts: 128
Followers: 0

Kudos [?]: 28 [0], given: 110

GMAT ToolKit User
Re: [#permalink] New post 19 Oct 2013, 18:54
christoph wrote:
xennie wrote:
Where did you get it from? Might be useful to memorize a few of those formulas for the actual exam.


here are some useful formulas...


The attachment is written with invisible ink :lol:
i cant see anything..pls can you upload it again thanks :)
_________________

“Confidence comes not from always being right but from not fearing to be wrong.”

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 23409
Followers: 3613

Kudos [?]: 28940 [0], given: 2871

Re: Re: [#permalink] New post 20 Oct 2013, 02:56
Expert's post
ankur1901 wrote:
christoph wrote:
xennie wrote:
Where did you get it from? Might be useful to memorize a few of those formulas for the actual exam.


here are some useful formulas...


The attachment is written with invisible ink :lol:
i cant see anything..pls can you upload it again thanks :)


This attachment is lost.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

COLLECTION OF QUESTIONS:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS ; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
25 extra-hard Quant Tests

Get the best GMAT Prep Resources with GMAT Club Premium Membership

Re: Re:   [#permalink] 20 Oct 2013, 02:56
    Similar topics Author Replies Last post
Similar
Topics:
14 A 100-litre mixture of milk and water contains 36 litres of alphonsa 14 26 Aug 2014, 23:28
1 Experts publish their posts in the topic In a mixture of 45 litres the ratio of milk to water antoxavier 1 21 Feb 2013, 07:00
2 Experts publish their posts in the topic A mixture of 40 liters of milk and water contains 10% water. munia123 8 27 Oct 2010, 11:57
5 Two mixtures A and B contain milk and water in the ratios bmwhype2 20 02 Jan 2008, 06:16
2 vessels contain mixture of water and milk in the ratio 1:2 rxs0005 3 02 Jan 2005, 08:19
Display posts from previous: Sort by

A 20 litre mixture of milk and water contains milk and water

  Question banks Downloads My Bookmarks Reviews Important topics  


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®.