It is currently 18 Dec 2017, 10:47

# Final Week of R1 Decisions:

CHAT Rooms | MIT Sloan | McCombs

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Mixture A is 20% oil and 80% material B by weight.

Author Message
TAGS:

### Hide Tags

Intern
Status: Gmat Beginner
Joined: 03 Aug 2013
Posts: 3

Kudos [?]: 18 [2], given: 4

Location: India
GMAT 1: 730 Q50 V41
GPA: 3.71
Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

06 Aug 2013, 07:55
2
KUDOS
11
This post was
BOOKMARKED
00:00

Difficulty:

55% (hard)

Question Stats:

71% (02:57) correct 29% (02:34) wrong based on 241 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

Can someone please explain the solution to this problem...
[Reveal] Spoiler: OA

Last edited by Zarrolou on 06 Aug 2013, 08:00, edited 1 time in total.
Edited the question, renamed the topic.

Kudos [?]: 18 [2], given: 4

VP
Status: Far, far away!
Joined: 02 Sep 2012
Posts: 1121

Kudos [?]: 2408 [2], given: 219

Location: Italy
Concentration: Finance, Entrepreneurship
GPA: 3.8
Re: Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

06 Aug 2013, 08:05
2
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 $$x=6$$

A

Hope 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 I-II- CR New SC set out !! , My Quant

Rules for Posting in the Verbal Forum - Rules for Posting in the Quant Forum[/size][/color][/b]

Kudos [?]: 2408 [2], given: 219

SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1848

Kudos [?]: 2794 [1], given: 193

Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

01 Oct 2014, 23:23
1
KUDOS
Oil ................ Material ................. Total

1.6 .................... 6.4 ........................... 8 (Initial Mix)

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

_________________

Kindly press "+1 Kudos" to appreciate

Kudos [?]: 2794 [1], given: 193

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7804

Kudos [?]: 18159 [2], given: 236

Location: Pune, India
Re: Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

18 Oct 2015, 22:53
2
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.

_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for \$199

Veritas Prep Reviews

Kudos [?]: 18159 [2], given: 236

Director
Joined: 05 Mar 2015
Posts: 966

Kudos [?]: 302 [0], given: 41

Re: Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

21 May 2016, 09:29
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=(A2-Avg)/(Avg-A1)
(36-30)/(30-20)
6/10
means for every 10 kg of new mix. we need 6 kg of mix A
Ans A

Kudos [?]: 302 [0], given: 41

Director
Joined: 07 Dec 2014
Posts: 862

Kudos [?]: 297 [1], given: 17

Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

21 May 2016, 10:22
1
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, 18:23, edited 1 time in total.

Kudos [?]: 297 [1], given: 17

Senior Manager
Status: DONE!
Joined: 05 Sep 2016
Posts: 408

Kudos [?]: 26 [1], given: 283

Re: Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

27 Oct 2016, 17:31
1
KUDOS
0.20(8+x)+2=(10+x)(0.30)
3.6+0.20x=3+0.30x
0.6=0.10x
x=6

Kudos [?]: 26 [1], given: 283

Intern
Joined: 24 Jan 2016
Posts: 1

Kudos [?]: [0], given: 63

Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

05 Nov 2016, 18:23
hi there, i'm trying to solve this problem via the alligation method, but I'm stuck. Help is much appreciated!

A = 80-70= 10
B = 0 - 70 = 70
70:10

solution=7???

not sure why I'm getting this wrong.

Kudos [?]: [0], given: 63

Target Test Prep Representative
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1810

Kudos [?]: 996 [1], given: 5

Re: Mixture A is 20% oil and 80% material B by weight. [#permalink]

### Show Tags

22 Nov 2017, 11:28
1
KUDOS
Expert's post
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

_________________

Jeffery Miller

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Kudos [?]: 996 [1], given: 5

Re: Mixture A is 20% oil and 80% material B by weight.   [#permalink] 22 Nov 2017, 11:28
Display posts from previous: Sort by