It is currently 23 Oct 2017, 12:20

### 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

# Jackie has two solutions that are 2 percent sulfuric acid

Author Message
TAGS:

### Hide Tags

Intern
Joined: 02 Aug 2015
Posts: 44

Kudos [?]: 98 [4], given: 5

Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

20 Aug 2015, 19:27
4
KUDOS
31
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

79% (01:32) correct 21% (01:59) wrong based on 1013 sessions

### HideShow timer Statistics

Jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume, respectively. If these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid, approximately how many liters of the 2 percent solution will be required?

A) 18
B) 20
C) 24
D) 36
E) 42
[Reveal] Spoiler: OA

Kudos [?]: 98 [4], given: 5

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7677

Kudos [?]: 17405 [11], given: 232

Location: Pune, India
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

20 Aug 2015, 21:48
11
KUDOS
Expert's post
16
This post was
BOOKMARKED
Akgmat85 wrote:
Jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume, respectively. If these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid, approximately how many liters of the 2 percent solution will be required?

A) 18
B) 20
C) 24
D) 36
E) 42

Use weighted average:

2% and 12% solutions mix to give 5% solution.

w1/w2 = (A2 - Aavg)/(Aavg - A1) = (12 - 5)/(5 - 2) = 7/3

You need 7 parts of 2% solution and 3 parts of 12% solution to get 10 parts of 5% solution.
If total 5% solution is actually 60 litres, you need 7*6 = 42 litres of 2% solution and 3*6 = 18 litres of 12% solution.

The formula and its application in mixtures are discussed in the following two posts:
http://www.veritasprep.com/blog/2011/03 ... -averages/
http://www.veritasprep.com/blog/2011/04 ... -mixtures/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Kudos [?]: 17405 [11], given: 232 Intern Joined: 02 Jul 2015 Posts: 17 Kudos [?]: 19 [7], given: 45 Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 24 Aug 2015, 06:18 7 This post received KUDOS 3 This post was BOOKMARKED let a=amount of 2% acid and b= amount of 12% acid. Now, The equation translates to, 0.02a + .12b = .05(a+b) but a+b= 60 therefore .02a + .12b = .05(60) => 2a + 12b = 300 but b=60-a therefore 2a+ 12(60-a) = 300 => 10a = 420 hence a = 42. Kudos [?]: 19 [7], given: 45 Manager Joined: 07 Apr 2015 Posts: 180 Kudos [?]: 68 [4], given: 185 Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 24 Aug 2015, 08:17 4 This post received KUDOS $$0,02*x + 0,12 * (60-x) = 0,05 * 60$$ $$0,02*x + 7,2 - 0,12*x = 3$$ $$4,2 = 0,1*x$$ $$x = 0,42$$ = 42% Last edited by noTh1ng on 25 Aug 2015, 07:34, edited 1 time in total. Kudos [?]: 68 [4], given: 185 Intern Joined: 24 Aug 2015 Posts: 8 Kudos [?]: 2 [1], given: 0 Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 24 Aug 2015, 11:19 1 This post received KUDOS Alright I'm so frustrated but after reading the article she posted. I try my best to answer using my way of thinking: 7 cups + 3 cups = 10 cups..so you need 10 cups of 5% solution to produce 60 liters. There is 10 cups and there is 60 liters. We have 60, we have 10 so the other number is missing is 6 therefore 6*7 cups = 42 liters of solution Kudos [?]: 2 [1], given: 0 Senior Manager Joined: 15 Sep 2011 Posts: 358 Kudos [?]: 405 [0], given: 45 Location: United States WE: Corporate Finance (Manufacturing) Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 24 Aug 2015, 17:49 blendercroix wrote: Alright I'm so frustrated but after reading the article she posted. I try my best to answer using my way of thinking: 7 cups + 3 cups = 10 cups..so you need 10 cups of 5% solution to produce 60 liters. There is 10 cups and there is 60 liters. We have 60, we have 10 so the other number is missing is 6 therefore 6*7 cups = 42 liters of solution Hi blendercroix, She got the 6 because it's the unknown multiplier of the ratio of 3x:7x. That is, $$3x + 7x = 10x$$, and 10x into $$60$$ is $$6$$. Six isn't a value but what helps calculate the ratio. Anyhow, it seems your logic is similar to what she posted, but instead of $$x$$ you made the unknown multiplier a "cup." Kr, Mejia Last edited by mejia401 on 25 Aug 2015, 03:33, edited 1 time in total. Kudos [?]: 405 [0], given: 45 Veritas Prep GMAT Instructor Joined: 16 Oct 2010 Posts: 7677 Kudos [?]: 17405 [1], given: 232 Location: Pune, India Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 24 Aug 2015, 21:01 1 This post received KUDOS Expert's post blendercroix wrote: Alright I'm so frustrated but after reading the article she posted. I try my best to answer using my way of thinking: 7 cups + 3 cups = 10 cups..so you need 10 cups of 5% solution to produce 60 liters. There is 10 cups and there is 60 liters. We have 60, we have 10 so the other number is missing is 6 therefore 6*7 cups = 42 liters of solution Yes, you are right. Look, for every 10 cups/liters/ml/gallons/units etc of 5% solution, you need 7 cups/liters/ml/gallons/units etc of 2% solution and 3 cups/liters/ml/gallons/units etc of 12% solution. So for each 10 litres of 5% solution, you need 7 litres of 2% and 3 litres of 12%. Then how much will you need for 60 litres of 5% solution? You will need 6 times the original quantity so you will need 7*6 = 42 litres of 2% solution and 3*6 = 18 litres of 12% solution. _________________ Karishma Veritas Prep | GMAT Instructor My Blog Get started with Veritas Prep GMAT On Demand for$199

Veritas Prep Reviews

Kudos [?]: 17405 [1], given: 232

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7677

Kudos [?]: 17405 [0], given: 232

Location: Pune, India
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

24 Aug 2015, 21:04
blendercroix wrote:
Alright I'm so frustrated but after reading the article she posted. I try my best to answer using my way of thinking:

7 cups + 3 cups = 10 cups..so you need 10 cups of 5% solution to produce 60 liters. There is 10 cups and there is 60 liters. We have 60, we have 10 so the other number is missing is 6 therefore 6*7 cups = 42 liters of solution

Take a look at the ratios post: http://www.veritasprep.com/blog/2011/03 ... of-ratios/
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199 Veritas Prep Reviews Kudos [?]: 17405 [0], given: 232 Manager Joined: 30 Dec 2015 Posts: 90 Kudos [?]: 20 [2], given: 153 GPA: 3.92 WE: Engineering (Aerospace and Defense) Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 16 Jan 2016, 22:36 2 This post received KUDOS 3 This post was BOOKMARKED For a question like this always have 2 equations, one for concentration and one for volume: Let X = vol of 2% sol Y = vol of 12% sol Since both solutions are mixed to make 60liters of 5% solution X + Y = 60 ----1 Also, equation for concentration 2X + 12Y = 5 (60) 2X + 12Y = 300 ------2 Solve equation 1 & 2 simultaneously Y = 18 X = 60-18 = 42 _________________ If you analyze enough data, you can predict the future.....its calculating probability, nothing more! Kudos [?]: 20 [2], given: 153 Manager Joined: 08 Sep 2015 Posts: 73 Kudos [?]: 40 [2], given: 29 Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 14 Feb 2017, 23:21 2 This post received KUDOS 2% 12% 5% 7% 3% => we need 7 parts of the 2% solution and 3 parts of the 12% solution => total 10 parts => 60/10 = 3 liters Therefore, 7 * 3 liters = 42 liters of 2% solution is needed. Kudos [?]: 40 [2], given: 29 EMPOWERgmat Instructor Status: GMAT Assassin/Co-Founder Affiliations: EMPOWERgmat Joined: 19 Dec 2014 Posts: 9990 Kudos [?]: 3423 [3], given: 172 Location: United States (CA) GMAT 1: 800 Q51 V49 GRE 1: 340 Q170 V170 Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink] ### Show Tags 16 Feb 2017, 14:00 3 This post received KUDOS Expert's post 1 This post was BOOKMARKED Hi All, This is essentially a Weighted Average question, but it can be solved in a variety of different ways. Since the answer choices are "spread out" numbers, there's actually a great 'brute force' approach that you can use to logically answer this question without doing that much math. We're told to mix a 2% acid solution with a 12% acid solution and end up with 60 LITERS of 5% acid solution. We're asked how many liters (of the 60) would be the 2% solution. IF.... we had 1 liter of each solution, then the acidity of the mixture would be (2% + 12%)/2 = 7%.... this is clearly too high (it's supposed to be 5%), so we need MORE of the 2% mixture. IF.... we had 2 liters of the 2% solution and 1 liter of the 12% solution, then the acidity of the mixture would be (2% + 2% + 12%)/3 = 16/3% = 5 1/3%.... this is also clearly too high (it's supposed to be 5%), so we need even MORE of the 2% mixture. In this example, it's worth noting that 2/3 of the mixture is the 2% solution. Since we need even MORE of that solution, we need MORE than 2/3 of the total to be that 2% mixture. There's only one answer that's more than 2/3 of 60.... Final Answer: [Reveal] Spoiler: E GMAT assassins aren't born, they're made, Rich _________________ 760+: Learn What GMAT Assassins Do to Score at the Highest Levels Contact Rich at: Rich.C@empowergmat.com # Rich Cohen Co-Founder & GMAT Assassin Special Offer: Save$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

***********************Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!***********************

Kudos [?]: 3423 [3], given: 172

Director
Joined: 07 Dec 2014
Posts: 817

Kudos [?]: 249 [1], given: 12

Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

16 Feb 2017, 17:56
1
KUDOS
blockman wrote:
Jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume, respectively. If these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid, approximately how many liters of the 2 percent solution will be required?

A) 18
B) 20
C) 24
D) 36
E) 42

let x=liters of 2% solution needed
.02x+.12(60-x)=.05*60
x=42 liters

Kudos [?]: 249 [1], given: 12

Intern
Joined: 19 Jul 2016
Posts: 14

Kudos [?]: 17 [1], given: 51

Location: Moldova, Republic of
Concentration: Strategy, Operations
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

22 May 2017, 13:01
1
KUDOS
1
This post was
BOOKMARKED

Kudos [?]: 17 [1], given: 51

SVP
Joined: 12 Sep 2015
Posts: 1798

Kudos [?]: 2476 [1], given: 357

Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

10 Aug 2017, 12:36
1
KUDOS
Expert's post
Top Contributor
blockman wrote:
Jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume, respectively. If these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid, approximately how many liters of the 2 percent solution will be required?

A) 18
B) 20
C) 24
D) 36
E) 42

Weighted average of groups combined = (group A proportion)(group A average) + (group B proportion)(group B average) + (group C proportion)(group C average) + ...

Let x be the number of liters of 2% solution in the mixture
Since there are 60 liters in total, 60 - x will equal number of liters of 12% solution in the mixture

Now apply the formula:
5 = (x/60)(2) + [(60-x)/60](12)
Multiply both sides by 60 to get: 300 = 2x + (60-x)(12)
Expand: 300 = 2x + 720 - 12x
Rearrange: -420 = -10x
Solve: x = 42

RELATED VIDEO

_________________

Brent Hanneson – Founder of gmatprepnow.com

Kudos [?]: 2476 [1], given: 357

SVP
Joined: 12 Sep 2015
Posts: 1798

Kudos [?]: 2476 [0], given: 357

Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

10 Aug 2017, 12:49
Expert's post
Top Contributor
blockman wrote:
Jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume, respectively. If these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid, approximately how many liters of the 2 percent solution will be required?

A) 18
B) 20
C) 24
D) 36
E) 42

Another approach is to keep track of the acid
Let x = number of liters of 2% solution needed
So, 60 - x = number of liters of 12% solution needed

2% of x = 0.02x
So, 0.02x = the number of liters of PURE acid in the 2% solution

12% of 60 - x = 0.12(60 - x) = 7.2 - 0.12x
So, 7.2 - 0.12x = the number of liters of PURE acid in the 12% solution

Now let's COMBINE the two solutions.
Total volume of PURE acid = 0.02x + 7.2 - 0.12x
= 7.2 - 0.1x
So, our NEW solution contains 7.2 - 0.1x liters of PURE acid
Also, the NEW solution has a total volume of 60 liters

Since the NEW solution is 5% PURE acid, we can write: (7.2 - 0.1x)/60 = 5/100
Cross multiply to get: 100(7.2 - 0.1x) = 5(60)
Expand: 720 - 10x = 300
Add 10 x to both sides: 720 = 300 + 10x
Subtract 300 from both sides: 420 = 10x
Solve: x = 42

[Reveal] Spoiler:
E

RELATED VIDEO

_________________

Brent Hanneson – Founder of gmatprepnow.com

Kudos [?]: 2476 [0], given: 357

Director
Joined: 07 Dec 2014
Posts: 817

Kudos [?]: 249 [0], given: 12

Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

11 Aug 2017, 12:14
blockman wrote:
Jackie has two solutions that are 2 percent sulfuric acid and 12 percent sulfuric acid by volume, respectively. If these solutions are mixed in appropriate quantities to produce 60 liters of a solution that is 5 percent sulfuric acid, approximately how many liters of the 2 percent solution will be required?

A) 18
B) 20
C) 24
D) 36
E) 42

let x=liters of 2% solution needed
.02x+.12y=.05(x+y)
x/y=7/3
x=7/10*60=42 liters
E

Kudos [?]: 249 [0], given: 12

Manager
Joined: 06 Jul 2014
Posts: 105

Kudos [?]: 39 [0], given: 179

Location: India
Concentration: Finance, Entrepreneurship
GMAT 1: 640 Q48 V30
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

11 Aug 2017, 12:24
Quantity of Cheaper / Quantity of Dearer= CP of Dearer – Mean Price / Mean Price – CP of Cheaper

Quantity of Cheaper +Quantity of Dearer=60

CP of Dearer – Mean Price / Mean Price – CP of Cheaper= 12-5/5-2=7/3=7/10*60=42

Kudos [?]: 39 [0], given: 179

Intern
Joined: 18 May 2017
Posts: 16

Kudos [?]: 0 [0], given: 116

WE: Corporate Finance (Health Care)
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

20 Sep 2017, 12:02
.02A +.12B=.05(A+B)
2A+12B=5A+5B
7B=3A
7/3 = A/B
7*6=42

Kudos [?]: 0 [0], given: 116

Senior Manager
Joined: 04 Sep 2016
Posts: 319

Kudos [?]: 67 [0], given: 201

Location: India
WE: Engineering (Other)
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

26 Sep 2017, 06:15
VeritasPrepKarishma

Can you please explain solution posted by EugeneFish?
I went through your blog here
but all I am able to proceed beyond assigning two points (weights) on line segment and invert distance from either of them.
say w1/w2 = d2/d1

Kudos [?]: 67 [0], given: 201

Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 7677

Kudos [?]: 17405 [0], given: 232

Location: Pune, India
Re: Jackie has two solutions that are 2 percent sulfuric acid [#permalink]

### Show Tags

27 Sep 2017, 03:10
VeritasPrepKarishma

Can you please explain solution posted by EugeneFish?
I went through your blog here
but all I am able to proceed beyond assigning two points (weights) on line segment and invert distance from either of them.
say w1/w2 = d2/d1

EugeneFish has given the pictorial representation of the scale method.

You should check out this post instead: https://www.veritasprep.com/blog/2011/0 ... -averages/

It discusses the scale method, why it works and its pictorial and formula depiction.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

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

Veritas Prep Reviews

Kudos [?]: 17405 [0], given: 232

Re: Jackie has two solutions that are 2 percent sulfuric acid   [#permalink] 27 Sep 2017, 03:10

Go to page    1   2    Next  [ 21 posts ]

Display posts from previous: Sort by