GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 23 Oct 2019, 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

# A 30% solution of barium chloride is mixed with 10 grams of water to f

Author Message
TAGS:

### Hide Tags

Intern
Joined: 05 Mar 2011
Posts: 3
A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

Updated on: 27 Oct 2014, 02:12
2
9
00:00

Difficulty:

35% (medium)

Question Stats:

72% (01:48) correct 28% (02:13) wrong based on 216 sessions

### HideShow timer Statistics

A 30% solution of barium chloride is mixed with 10 grams of water to form a 20% solution. How many grams of original solution did we start with ?

A) 10
B) 15
C) 20
D) 25
E) 30

I am trained to complete above problem as per following technique. Is it possible to solve in following manner.

30%_________100%

______20%

ratio is 100-20 : 20-30, which is wrong. There should not be 20. Instead, value in the middle should be in between 30% to 100%.

Is there any way to solve above problem as per technique.?

Thank you

Originally posted by acc1444 on 27 Oct 2014, 00:06.
Last edited by Bunuel on 27 Oct 2014, 02:12, edited 2 times in total.
Renamed the topic and edited the question.
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1747
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

27 Oct 2014, 21:25
4
3
Algebraic way:

Say x gms of barium chloride solution mixed with water

$$\frac{30}{100} x + 0 * 10$$ ............. (1)

Resultant is 20% of barium chloride

$$\frac{20}{100} (x + 10)$$ ................. (2)

Equating (1) & (2)

$$\frac{30}{100} x + 0 * 10 = \frac{20}{100} (x + 10)$$

x = 20

_________________
Kindly press "+1 Kudos" to appreciate
##### General Discussion
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1747
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

27 Oct 2014, 21:04
1
acc1444 wrote:
A 30% solution of barium chloride is mixed with 10 grams of water to form a 20% solution. How many grams of original solution did we start with ?

A) 10
B) 15
C) 20
D) 25
E) 30

I am trained to complete above problem as per following technique. Is it possible to solve in following manner.

30%_________100%

______20%

ratio is 100-20 : 20-30, which is wrong. There should not be 20. Instead, value in the middle should be in between 30% to 100%.

Is there any way to solve above problem as per technique.?

Thank you

10 grams of water means 0% of barium chloride solution

Take it in this way.....

30% _________ 0%

______ 20% ................

20 - 0= 20 ............. 30-20 = 10

_________________
Kindly press "+1 Kudos" to appreciate
Manager
Joined: 03 Jan 2015
Posts: 58
Concentration: Strategy, Marketing
WE: Research (Pharmaceuticals and Biotech)
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

11 Jan 2015, 01:13
3
Let X gm be the starting solution
For 30% solution, the amount of BaCl in gm = 0.3X gm ----- (I)

Now, 10 g of H2O was added to the solution. Therefore the new quantity of solution =(X + 10) gm
This gives 20% solution. Hence the amount of BaCl in gm the new solution = 0.2 (X + 10) gm ----- (II)

Note that no new BaCl has been added. Hence the amount of BaCl should remain the same. Hence, we can equate I and II

0.3X = 0.2 (X + 10)
0.3X = 0.2X + 2
0.1X = 2
Manager
Joined: 27 Oct 2013
Posts: 198
Location: India
Concentration: General Management, Technology
GMAT Date: 03-02-2015
GPA: 3.88
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

11 Jan 2015, 05:34
3
just deal with unchanged quantities -> here unchanged quantity is Barium Chloride

Say original solution = X
New solution will be X + 10

Barium Chloride remains same in both the solution

0.3(X) = 0.2(X + 10)

0.1X = 2

X = 20
EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 15316
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

11 Jan 2015, 17:24
Hi All,

These types of "weighted" average questions can be solved in a few different ways. You can use the Weighted Average formula, you can use Allegation (which is a ratio-based approach) and (at least in this question) you can TEST THE ANSWERS....

We're told that 10g of water are mixed with an unknown amount of 30% barium mixture to form a 20% barium final mixture. We're asked to figure out how much barium mixture we have....

Logically, if we had 10g of water mixed with 10g of barium mixture, we'd end up with a 15% overall mixture, so 10 is NOT the answer. We need MORE barium mixture to raise the final mixture up to 20%. Since the numbers in the prompt are all "round" numbers, it's highly likely that the correct answer will ALSO be a round number....

Let's TEST Answer C = 20g

(20g of barium mixture)(30% barium) = 6g barium
+ 10g water.....

(6g barium)/(30g total liquid) = .2 = 20% final barium mixture.

So, the initial barium mixture MUST be 20g

GMAT assassins aren't born, they're made,
Rich
_________________
Contact Rich at: Rich.C@empowergmat.com

The Course Used By GMAT Club Moderators To Earn 750+

souvik101990 Score: 760 Q50 V42 ★★★★★
ENGRTOMBA2018 Score: 750 Q49 V44 ★★★★★
Manager
Joined: 03 Jan 2015
Posts: 58
Concentration: Strategy, Marketing
WE: Research (Pharmaceuticals and Biotech)
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

13 Jan 2015, 16:05
1
1
Another quick way for these type of problems:

(old - new)/new = dilution
(30-20)/(20) = 1/2 = dilution = 10 gm
So, original solution = (1/2)*10 gm = 20 gm
Manager
Joined: 16 Mar 2016
Posts: 121
Location: France
GMAT 1: 660 Q47 V33
GPA: 3.25
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

04 Jun 2016, 04:27
Let's x be the original quantity

we have 20%(10+x) = 30%(x)
200 + 20x = 30x
x=20
Current Student
Joined: 18 Oct 2014
Posts: 801
Location: United States
GMAT 1: 660 Q49 V31
GPA: 3.98
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

04 Jun 2016, 09:02
acc1444 wrote:
A 30% solution of barium chloride is mixed with 10 grams of water to form a 20% solution. How many grams of original solution did we start with ?

A) 10
B) 15
C) 20
D) 25
E) 30

I am trained to complete above problem as per following technique. Is it possible to solve in following manner.

30%_________100%

______20%

ratio is 100-20 : 20-30, which is wrong. There should not be 20. Instead, value in the middle should be in between 30% to 100%.

Is there any way to solve above problem as per technique.?

Thank you

70% water (x gm) is mixed with 100% water (10gm) to give 80% water solution

x/10= 100-80/ 80-70= 20/10

x= 20
_________________
I welcome critical analysis of my post!! That will help me reach 700+
Intern
Joined: 28 Dec 2015
Posts: 37
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

07 Jun 2016, 03:19
Simplest way is weighted average:Just remember that water has a 0% concentration.

and use the weighted average formula:
C1V1+C2V2/V1+V2=Final concentration.

0.3x+10*0/x+10=0.2

Solving,x=20.
Current Student
Status: DONE!
Joined: 05 Sep 2016
Posts: 357
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

27 Oct 2016, 18:40
0.70x+10=0.80(10+x)
0.70x+10=8+0.80x
2=0.10x
x=20
Non-Human User
Joined: 09 Sep 2013
Posts: 13421
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f  [#permalink]

### Show Tags

29 Apr 2019, 01:15
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Re: A 30% solution of barium chloride is mixed with 10 grams of water to f   [#permalink] 29 Apr 2019, 01:15
Display posts from previous: Sort by