BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

Target Test Prep · GMAT

Choose how you want to prepare

Learn live with an expert or move at your own pace. Every option includes the complete TTP study system.

★★★★★5.0559 reviews
GMATLiveTeach Starts Oct 17
Chris Peckover, Target Test Prep GMAT expert
LIVE ONLINE CLASSES

Get Ready for GMAT Test Day Faster with Live Online Classes

with Chris Peckover, 100th-Percentile GMAT Scorer

Oct 17 · Chris Peckover
Sat · 11:00 AM to 2:00 PM ET
Oct 20 · Chris Peckover
Tue, Thu · 8:00 to 10:00 PM ET
Oct 25 · Josh Braslow
Sun · 1:00 to 4:00 PM ET
Included
40 hours of live online classes + 6 months of TTP OnDemand
  • Attend the first class for free
  • Every class is recorded, so you never fall behind
View classes & enroll
Limited seats availableTarget Test Prep
EALiveTeachOnDemand 5 seats left Start anytime
EXECUTIVE ASSESSMENT

Target Test Prep EA OnDemand

Self-paced EA prep. Study on your schedule.

Logan Thompson
EXECUTIVE ASSESSMENT

Sep 6 to Dec 6, 2026

with Logan Thompson

165+ EA score guarantee
$05-day trial no automatic billing
Schedule
Sun · 9:30 AM to 12:30 PM ET
Included
40 hours of live online classes plus six months of access to the complete TTP EA OnDemand course.
  • 165+ EA Score Guarantee
  • 4,100+ Quant, Verbal, and Integrated Reasoning practice questions
  • 400+ hours of in-depth video lessons
  • 3,000+ step-by-step video solutions
View EA class & enroll Start free 5-day trial
Limited cohort · enrollment openTrial includes full course accessTarget Test Prep
GMATOnDemand Start anytime
SELF-PACED MASTERCLASS

Target Test Prep GMAT OnDemand

Complete access from day one. Study on your schedule.

715+ score guarantee
$0to start then $127/mo
  • Personalized study plan and analytics
  • Thousands of lessons and practice questions
Start free 5-day trial
Read 559 reviewsTarget Test Prep

Compare the format, schedule, and included access before enrolling. Prices and seat counts shown reflect the supplied offer details.

Alligation?

Expert replies
Post new topic Post Reply
Previous Topic Next Topic
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Mon Jan 24, 2011 1:37 pm
by madhan_dc » Wed Feb 23, 2011 3:00 pm
A container contains 40 litres of milk. From this container 4 litres of milk was taken away and replaced by water.
This process was repeated further 2 times. How much milk is contained by the container.

This is what i thought:
Milk water
begin 40 0
1st 36 4
2nd 32 8
3rd 28 12

so the answer is 28.

But the answer is 29.16 and i cant seem to understand how. It would be great if someone can shed some light.

thanks.
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Source: — Problem Solving |
Legendary Member
Posts: 1337
Joined: Sat Dec 27, 2008 6:29 pmFollowed by: 10 members
Thanked: 127 times

by Night reader » Wed Feb 23, 2011 4:25 pm
10% decrease in milky concentration three times makes --> 1*0.9*0.9*0.9
40 lt milk *1*0.9*0.9*0.9 = 29.16 :)
simple as my five fingers' count/says process...
madhan_dc wrote:A container contains 40 litres of milk. From this container 4 litres of milk was taken away and replaced by water.
This process was repeated further 2 times. How much milk is contained by the container.

This is what i thought:
Milk water
begin 40 0
1st 36 4
2nd 32 8
3rd 28 12

so the answer is 28.

But the answer is 29.16 and i cant seem to understand how. It would be great if someone can shed some light.

thanks.
My knowledge frontiers came to evolve the GMATPill's methods - the credited study means to boost the Verbal competence. I really like their videos, especially for RC, CR and SC. You do check their study methods at https://www.gmatpill.com
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Master | Next Rank: 500 Posts
Posts: 139
Joined: Fri Nov 26, 2010 4:45 pmFollowed by: 1 member
Location: Boston
Thanked: 20 times
GMAT Score:720

by stormier » Wed Feb 23, 2011 4:31 pm
madhan_dc wrote:A container contains 40 litres of milk. From this container 4 litres of milk was taken away and replaced by water.
This process was repeated further 2 times. How much milk is contained by the container.

This is what i thought:
Milk water
begin 40 0
1st 36 4
2nd 32 8
3rd 28 12

so the answer is 28.

But the answer is 29.16 and i cant seem to understand how. It would be great if someone can shed some light.

thanks.
When you remove 4 liter the second time - you will remove some of the milk as well - and that's the mistake in your calculation

Let's look at just the water in the container - remember that the total volume remains 40.

Water after Step 1 = 4 _______________________ (36M,4W)
Water after Step 2 = 4 - 0.1*4 + 4 = 7.6__________ (32.4M,7.6W)
Water after Step 3 = 7.6 - 0.1*7.6 + 4 = 10.84 ___ (29.16M,10.84W)

When you remove 4 liter (or 10 % of 40 liter) of a 36:4 mixture, you remove 10% of 4 liter water.

Thus milk = 40 - 10.84 = 29.16
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY

GMAT/MBA Expert

User avatar
GMAT Instructor
Posts: 1179
Joined: Sun Apr 11, 2010 9:07 pmFollowed by: 88 members
Location: Milpitas, CA
Thanked: 447 times

by Rahul@gurome » Fri Feb 25, 2011 9:44 pm
Solution:
The container has 40 liters of milk.
From this, 4 liters of milk was taken away and replaced with water.
So, now we have 36 liters of milk and 4 liters of water.
Hence the new mixture has milk and water in the ratio 36:4 or 9:1.
So, now if we withdraw 4 liters, the remaining 36 liters has 36*9/10 liters milk and 36*1/10 liters water.
Again, when we add 4 liters of water, amount of milk is 36*9/10 and the amount of water is 36*1/10 + 4 or 76/10 liters.
Hence, now the mixture has milk and water in the ratio 36*9 : 76 or 81 : 19.
Again, 4 liters is being withdrawn.
Or 36 liters of mixture is left.
So now amount of milk is 36*81/100 = 29.16 liters.
Rahul Lakhani
Quant Expert
Gurome, Inc.
https://www.GuroMe.com
On MBA sabbatical (at ISB) for 2011-12 - will stay active as time permits
1-800-566-4043 (USA)
+91-99201 32411 (India)
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Junior | Next Rank: 30 Posts
Posts: 11
Joined: Tue Nov 09, 2010 7:23 pm
Thanked: 1 times

by gary391 » Sun Mar 13, 2011 8:00 am
We also have a formula for solving these type of problems:

Formula: If a Jar contains 'a' litres of liquid 'A', and if 'b' litres is withdrawn and replaced by liquid 'B',... Now again a if 'b' litres of mixture is withdrawn and replaced by liquid B, and the operation is repeated 'n' number of times in all, then:

LIQUID A LEFT IN JAR AFTER Nth OPERATION/INITIAL QUANTITY OF LIQUID A IN JAR= (a-b/a)^n

Gaurav
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Newbie | Next Rank: 10 Posts
Posts: 6
Joined: Thu May 17, 2012 11:33 am

by Liarish » Fri Sep 07, 2012 2:09 am
You are right Gary. We could also simply use compound interest formula. without going through so many steps.
A=P(1+r/100)^t

A=40(1-10/100)^3 We are subtracting here instead of adding as we are taking out a fixed quantity every month. So the final Amount will actually be less than 40. When solved, A= 29.16.

Oops, just realized my post came about a year and a half after the previous post. Never mind, hope someone will find it useful
Top
Join the discussion
Log in to postLogin with Googleuse password
QUOTE IN REPLY
Post new topic Post Reply
• Page 1 of 1