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

It is currently 26 Nov 2014, 07:15

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

m25,#30

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
Intern
Intern
avatar
Joined: 14 Feb 2013
Posts: 3
GMAT 1: Q V
GPA: 3.12
Followers: 0

Kudos [?]: 6 [0], given: 8

Re: m25,#30 [#permalink] New post 01 Oct 2013, 10:35
is there a way to solve this problem using allegations?
Expert Post
1 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 24117
Followers: 3737

Kudos [?]: 31302 [1] , given: 3345

Re: m25,#30 [#permalink] New post 02 Oct 2013, 01:39
1
This post received
KUDOS
Expert's post
Intern
Intern
avatar
Joined: 14 Feb 2013
Posts: 3
GMAT 1: Q V
GPA: 3.12
Followers: 0

Kudos [?]: 6 [0], given: 8

Re: m25,#30 [#permalink] New post 02 Oct 2013, 07:41
oh I see the explanation now. Thanks for the help on this problem. There are so many ways to solve these types of problems and I want to develop a strategy to always approach them in the most efficient manner.

Kudos(?) to both of you.
Intern
Intern
User avatar
Joined: 21 Jul 2014
Posts: 22
Followers: 0

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

GMAT ToolKit User CAT Tests
Re: m25,#30 [#permalink] New post 01 Sep 2014, 08:52
ritula wrote:
Some part of a 50% solution of acid was replaced with an equal amount of 30% solution of acid. If, as a result, 40% solution of acid was obtained, what part of the original solution was replaced?

(A) \frac{1}{5}
(B) \frac{1}{4}
(C) \frac{1}{2}
(D) \frac{3}{4}
(E) \frac{4}{5}

[Reveal] Spoiler: OA
C

Source: GMAT Club Tests - hardest GMAT questions

Can sum1 give a simpler explanation?


Solved it by plugging in the option C first :

If 1/2 of the original solution is replaced, that means 50 out of 100 was replaced.
so the replaced part will not have 30% of 50= 15units of acid
the remaining 50 units of the original solution (which was not replaced) has 50% = 25 units of acid
total we have 25+15=40% which is equal to the goal for plugging in ! bingo.. C is the answer !!

Bunuel, please comment if this is an OK approach to solve the question?
Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 24117
Followers: 3737

Kudos [?]: 31302 [0], given: 3345

Re: m25,#30 [#permalink] New post 01 Sep 2014, 09:04
Expert's post
apsForGmat wrote:
ritula wrote:
Some part of a 50% solution of acid was replaced with an equal amount of 30% solution of acid. If, as a result, 40% solution of acid was obtained, what part of the original solution was replaced?

(A) \frac{1}{5}
(B) \frac{1}{4}
(C) \frac{1}{2}
(D) \frac{3}{4}
(E) \frac{4}{5}

[Reveal] Spoiler: OA
C

Source: GMAT Club Tests - hardest GMAT questions

Can sum1 give a simpler explanation?


Solved it by plugging in the option C first :

If 1/2 of the original solution is replaced, that means 50 out of 100 was replaced.
so the replaced part will not have 30% of 50= 15units of acid
the remaining 50 units of the original solution (which was not replaced) has 50% = 25 units of acid
total we have 25+15=40% which is equal to the goal for plugging in ! bingo.. C is the answer !!

Bunuel, please comment if this is an OK approach to solve the question?


Yes, that's correct.
_________________

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

Take a Survey about GMAT Prep - Win Prizes!

Re: m25,#30   [#permalink] 01 Sep 2014, 09:04
Display posts from previous: Sort by

m25,#30

  Question banks Downloads My Bookmarks Reviews Important topics  

Go to page   Previous    1   2   [ 25 posts ] 

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®.