ration problem : GMAT Problem Solving (PS)

ration problem

Oldest

Best Reply

Author

Message

TAGS:

Manager

Status: GMAT Preperation

Joined: 04 Feb 2010

Posts: 105

Schools: HBS, Tuck

Followers: 1

Kudos [?]: 2 [0], given: 15

ration problem [#permalink]

29 Sep 2010, 00:19

00:00

Question Stats:

87% (03:52) correct

12% (01:50) wrong

based on 2 sessions

I am sure this will be easy for you guys.. but i had issues in understanding the explaination in OG, here goes the question:

qs 335 og10) the ratio, by volume, of soap to alcohol to water in a certain solution is 2.5.100. The solution will be altered so that the ratio of soap to alcohol is doubled while the ratio of soap to water is halfed. if the altered solution will contain 100 cubic cetimeters of alcohol, how many centemeters of water will it contain ?

50
200
400
625
800

I am getting 400
.. but the answer says 800 ?? can you explain what am i doing wrong here

S:A:W 2:50:100
new S:A 4:100
new S:W 1:100

if soap is if alcohol is 100 soap is 4 and water is 4*100= 400

[Reveal] Spoiler: OA

Kaplan Promo Code

Knewton GMAT Discount Codes

Manhattan GMAT Discount Codes

GMAT Club team member

Joined: 02 Sep 2009

Posts: 11565

Followers: 1796

Kudos [?]: 9571 [0], given: 826

Re: ration problem [#permalink]

29 Sep 2010, 00:41

vanidhar wrote:

I am sure this will be easy for you guys.. but i had issues in understanding the explaination in OG, here goes the question:

qs 335 og10) the ratio, by volume, of soap to alcohol to water in a certain solution is 2.50.100. The solution will be altered so that the ratio of soap to alcohol is doubled while the ratio of soap to water is halfed. if the altered solution will contain 100 cubic cetimeters of alcohol, how many centemeters of water will it contain ?

50
200
400
625
800

I am getting 400
.. but the answer says 800 ?? can you explain what am i doing wrong here

S:A:W 2:50:100
new S:A 4:100
new S:W 1:100

if soap is if alcohol is 100 soap is 4 and water is 4*100= 400

Given: \frac{s}{{\frac{a}{w}}}=\frac{2}{{\frac{50}{100}}};

The ratio of soap to alcohol is doubled --> \frac{s}{a}=2*\frac{2}{50}=\frac{4}{50};

The ratio of soap to water is halved --> \frac{s}{w}=\frac{1}{2}*\frac{2}{100}=\frac{1}{100}=\frac{4}{400};

New ratio: \frac{s}{{\frac{a}{w}}}=\frac{4}{{\frac{50}{400}}} --> \frac{a}{w}=\frac{50}{400} --> if a=2*50=100 then w=2*400=800.

Answer: E.
_________________

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

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. NEW!!!

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. NEW!!!

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

Find out what's new at GMAT Club - latest features and updates

Intern

Joined: 19 Dec 2009

Posts: 36

Followers: 0

Kudos [?]: 2 [0], given: 9

600-700 ratios problem [#permalink]

18 Oct 2010, 11:23

The ratio by volume of soap to alcohol to water is 2:50:100. The solution will be altered so that the ratio of soap to alcohol is doubled while the ratio of soap to water is halved. If the altered solution will contain 100 cubic centimeters of alcohol, how many cubic centimeters of water will it contain?

a 50
b 200
c 400
d 625
e 800

Manager

Joined: 08 Sep 2010

Posts: 242

Location: India

WE 1: 6 Year, Telecom(GSM)

Followers: 3

Kudos [?]: 39 [0], given: 21

Re: 600-700 ratios problem [#permalink]

18 Oct 2010, 12:05

rtaha2412 wrote:

Ratio of S:A:W is 2:50:100

means S/A=2/50=1/25 and A/W= 50/100=1/2 Hence S/W = 1/50

Now in the altered solution S'/A'=(1/25)*2=2/25
While S'/W'=(1/50)*(1/2)=1/100
Hence A'/W'=(1/100)/(2/25)=1/8=25/(8*25) = 25/200

Therefore S':A':W'= 2:25:200

Now let the volume of new solution is x ml.

Alcohol Content ={25/(2+25+200)}*x =100
Hence x =(100*227)/25=908 ml

Hence the water content in new solution = {200/(2+25+200)}*908 = 800

Hence answer is E.

Consider KUDOS if it helped u in some way.

Senior Manager

Joined: 10 Nov 2010

Posts: 270

Location: India

Concentration: Strategy, Operations

GMAT 1: 520 Q42 V19
GMAT 2: 540 Q44 V21

WE: Information Technology (Computer Software)

Followers: 4

Kudos [?]: 19 [0], given: 22

water [#permalink]

20 Feb 2011, 08:29

Pls chk the image

Attachments

RP.JPG [ 28.03 KiB | Viewed 667 times ]

_________________

The proof of understanding is the ability to explain it.

Manager

Joined: 14 Feb 2011

Posts: 203

Followers: 4

Kudos [?]: 42 [0], given: 3

Re: water [#permalink]

20 Feb 2011, 08:36

Initial ratio is S:A:W = 2:50:100
After changes, the ratio becomes 4:50:400 (as 2:50 is doubled so S becomes 4 units and 2:100 is halved, so new water units are 400 as new ratios need to be 2:200 or 4:400)
Now, If 50 corresponds to 100 cc, then 400 corresponds to 800 cc - Ans E

Math Forum Moderator

Joined: 20 Dec 2010

Posts: 2100

Followers: 108

Kudos [?]: 655 [0], given: 376

Re: water [#permalink]

20 Feb 2011, 09:13

2:50:100

\frac{2}{50} to be doubled \frac{2*2}{50} = \frac{4}{50}

\frac{2}{100} is to be halved \frac{2}{2*100} = \frac{2}{200} = \frac{2*2}{200*2} = \frac{4}{400}

New proportion
Soap:Alcohol:Water
4:50:400

Alcohol is 100cc: Double of 50
Thus entire proportion should be multiplied by 2

8:100:800

Ans: "E"
_________________

~fluke

Find out what's new at GMAT Club - latest features and updates

GMAT Club team member

Joined: 02 Sep 2009

Posts: 11565

Followers: 1796

Kudos [?]: 9571 [0], given: 826

Re: water [#permalink]

20 Feb 2011, 10:14

Merging similar topics.
_________________

Re: water [#permalink] 20 Feb 2011, 10:14

		Similar topics	Author	Replies	Last post
Similar Topics:		Arithmetic - Operations on rational numbers	above720	2	18 Jan 2007, 00:05
	1	Robots X, Y, and Z each assemble components at their	mrsmarthi	7	31 Mar 2009, 17:00
		How to graph rational inequalities??	Hussain15	5	28 Jan 2010, 09:54
		Rational Numbers	pclg	2	07 Feb 2010, 23:16
	1	Arithmetic operations on rational numbers problem	restore	3	15 Aug 2011, 15:30

ration problem

Main navigation

GMAT Resources

Partners

MBA Resources

GMAT ® is a registered trademark of the Graduate Management Admission Council ® (GMAC ®). GMAT Club's website has not been reviewed or endorsed by GMAC.

GMAT Courses

Admissions Consulting

ration problem

ration problem

Main navigation

GMAT Resources

Partners

MBA Resources