Author 
Message 
TAGS:

Hide Tags

Intern
Status: Gmat Beginner
Joined: 03 Aug 2013
Posts: 3
Location: India
sva: aditya
GPA: 3.71

Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
06 Aug 2013, 08:55
2
This post received KUDOS
13
This post was BOOKMARKED
Question Stats:
73% (03:04) correct 27% (02:31) wrong based on 296 sessions
HideShow timer Statistics
Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms of oil are added to the 8 kilograms mixture A, how many kilograms of mixture A must be added to make a 70% material B in the new mixture? A) 6 B) 7 C) 8 D) 9 E) 10
Official Answer and Stats are available only to registered users. Register/ Login.
Last edited by Bunuel on 05 Mar 2018, 10:03, edited 2 times in total.
Edited the question, renamed the topic.



VP
Status: Far, far away!
Joined: 02 Sep 2012
Posts: 1118
Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
06 Aug 2013, 09:05
4
This post received KUDOS
4
This post was BOOKMARKED
To the 8 kg of solution A (which has \(0.2*8\) kg of oil), 2 kg of oil are added, so the resulting percentage of oil is: \(\frac{0.2*8+2}{8+2}=\frac{3.6}{10}\), the resulting solution is 36% oil (3.6 kg) and 64% B (6.4 B). The \(x\) kg of mixture A that must be added to the new mixture, to obtain a 70% of B, is: \(\frac{6.4 + 0.8x}{10+x}=0.7\), \(6.4+0.8x=7+0.7x\) so \(x=6\) AHope everything is clear
_________________
It is beyond a doubt that all our knowledge that begins with experience.
Kant , Critique of Pure Reason Tips and tricks: Inequalities , Mixture  Review: MGMAT workshop Strategy: SmartGMAT v1.0  Questions: Verbal challenge SC III CR New SC set out !! , My QuantRules for Posting in the Verbal Forum  Rules for Posting in the Quant Forum[/size][/color][/b]



SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1838
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
02 Oct 2014, 00:23
1
This post received KUDOS
Oil ................ Material ................. Total 1.6 .................... 6.4 ........................... 8 (Initial Mix) After adding 2 units oil 3.6 ....................... 6.4 ........................ 10 Say "x" units of Initial mix is added to the new 3.6 ...................... \(6.4 + \frac{6.4x}{8}\) ................. 10+x Given that material has to be 70% in the new mix; setting up the equation accordingly \(\frac{70}{100} (10+x) = 6.4 + \frac{6.4x}{8}\) x = 6 Answer = A
_________________
Kindly press "+1 Kudos" to appreciate



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7988
Location: Pune, India

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
18 Oct 2015, 23:53
2
This post received KUDOS
Expert's post
1
This post was BOOKMARKED
sva2300 wrote: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms of oil are added to the 8 kilograms mixture A, how many kilograms of mixture A must be added to make a 70% material B in the new mixture?
A)6 B)7 C)8 D)9 E)10
Can someone please explain the solution to this problem... Use weighted averages concept discussed here: http://www.veritasprep.com/blog/2011/03 ... averages/http://www.veritasprep.com/blog/2011/04 ... mixtures/Old mix has 20% oil. You add 2 kgs of 100% oil. You get new mix with 30% oil (70% material B). w1/w2 = (100  30)/(30  20) = 70/10 = 7/1 For every 7 parts of mix A, you have added 1 part of oil. Since you have added 2 kgs oil, mix A must be 7*2 = 14 kgs. You already had 8 kgs of mix A, so extra mix A added must be 14  8 = 6 kgs. Answer (A)
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews



Director
Joined: 05 Mar 2015
Posts: 961

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
21 May 2016, 10:29
sva2300 wrote: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms of oil are added to the 8 kilograms mixture A, how many kilograms of mixture A must be added to make a 70% material B in the new mixture?
A)6 B)7 C)8 D)9 E)10
Can someone please explain the solution to this problem... Can be done with weighted avg method. if 2 kg more of oil is added to 20% oil of 8 kg mix,then a 10kg of mix will have 3.6kg (or 36%) of oil . A1=20(initial mix.) Avg. is what we need..ie 70% of material B means 30% of oil A2=36(36% of 10 kg mix) w1/w2=(A2Avg)/(AvgA1) (3630)/(3020) 6/10 means for every 10 kg of new mix. we need 6 kg of mix A Ans A



Director
Joined: 07 Dec 2014
Posts: 922

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
21 May 2016, 11:22
1
This post received KUDOS
let a=kilograms of mixture a to be added to new mixture total oil in new mixture will be 1.6+2+.2a=3.6+.2a kilograms total weight of new mixture will be 8+2+a=10+a kilograms (3.6+.2a)/(10+a)=.3 a=6 kilograms
Last edited by gracie on 06 Nov 2016, 19:23, edited 1 time in total.



Current Student
Status: DONE!
Joined: 05 Sep 2016
Posts: 405

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
27 Oct 2016, 18:31
2
This post received KUDOS
0.20(8+x)+2=(10+x)(0.30) 3.6+0.20x=3+0.30x 0.6=0.10x x=6



Intern
Joined: 24 Jan 2016
Posts: 1

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
05 Nov 2016, 19:23
hi there, i'm trying to solve this problem via the alligation method, but I'm stuck. Help is much appreciated!
A = 8070= 10 B = 0  70 = 70 70:10
solution=7???
not sure why I'm getting this wrong.



Target Test Prep Representative
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2116

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
22 Nov 2017, 12:28
sva2300 wrote: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms of oil are added to the 8 kilograms mixture A, how many kilograms of mixture A must be added to make a 70% material B in the new mixture?
A)6 B)7 C)8 D)9 E)10 Since mixture A is 8 kilograms by weight originally, it has 0.2(8) = 1.6 kilograms of oil and 0.8(8) = 6.4 kilograms of material B. After 2 more kilograms of oil are added, there will be 3.6 kilograms of oil but there will still be 6.4 kilograms of material B. Notice now we will have 10 kilograms of mixture A. If we let x = the number of kilograms of mixture A to be added, we are adding 0.8x kilograms of material B, thus we have: (6.4 + 0.8x)/(10 + x) = 0.7 6.4 + 0.8x = 7 + 0.7x 0.1x = 0.6 x = 6 Answer: A
_________________
Jeffery Miller
Head of GMAT Instruction
GMAT Quant SelfStudy Course
500+ lessons 3000+ practice problems 800+ HD solutions



Intern
Joined: 05 Dec 2017
Posts: 4
GPA: 3.35

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
05 Mar 2018, 09:59
Let say X Kg to be added, then, ATQ, 8 + 2 + x = (1.6 +2 +0.20X) + 0.70( 8+2+X) >10 + X = 10.6 + 0.90X > 0.10X = 0.60 > X = 6 Kg to be added
_________________
If you like my way of clarification, please give me one Kudo regards, Jamil_Mehedi



Intern
Joined: 11 Oct 2016
Posts: 4
Location: India

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
05 Mar 2018, 11:19
VeritasPrepKarishma : How can this question be solved by the allegation method?



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7988
Location: Pune, India

Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms [#permalink]
Show Tags
05 Mar 2018, 22:54
ishpreetanand wrote: VeritasPrepKarishma : How can this question be solved by the allegation method? I have solved it by allegation here: https://gmatclub.com/forum/mixtureais ... l#p1588660The formula depicts the allegation method.
_________________
Karishma Veritas Prep  GMAT Instructor My Blog
Get started with Veritas Prep GMAT On Demand for $199
Veritas Prep Reviews




Re: Mixture A is 20% oil and 80% material B by weight. If 2 more kilograms
[#permalink]
05 Mar 2018, 22:54






