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

It is currently 19 Apr 2019, 09:34

Close

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
Your Progress

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

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Close

Request Expert Reply

Confirm Cancel

A mixture consists of two spirits A and B; A evaporates at the rate of

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

 
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 54371
A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 05 Jul 2017, 00:27
00:00
A
B
C
D
E

Difficulty:

  45% (medium)

Question Stats:

64% (01:54) correct 36% (01:15) wrong based on 106 sessions

HideShow timer Statistics

A mixture consists of two spirits A and B; A evaporates at the rate of 2 ml per minute and B at 3 ml per minute. What will be the volume of the mixture after 10 minutes?

(1) Initial ratio of A and B in the mixture was 4 : 5.
(2) The final ratio of A and B in the mixture was 5 : 4.

_________________
Current Student
User avatar
P
Joined: 18 Aug 2016
Posts: 619
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
GMAT ToolKit User Reviews Badge
Re: A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 05 Jul 2017, 01:03
Bunuel wrote:
A mixture consists of two spirits A and B; A evaporates at the rate of 2 ml per minute and B at 3 ml per minute. What will be the volume of the mixture after 10 minutes?

(1) Initial ratio of A and B in the mixture was 4 : 5.
(2) The final ratio of A and B in the mixture was 5 : 4.


(1) gives us the initial ratio before evaporation happened

now in 10 mins A evaporated 20 ml and b evaporated 30 ml

if the initial ratio was 4/5 lets say the total volume was 9x and A:B was 4x:5x

Pre Evaporation
A : B ::: Total Volume
4x:5x ::: 9x
Post evaporation
A : B ::: Total Volume
4x-20:5x-30 ::: 9x-50
But we dont know the value of x hence Not sufficient

(2) gives us Post evaporation ratio
A : B ::: Total Volume
5y : 4y ::: 9y

Pre evaporation it was
A : B ::: Total Volume
5y+20 : 4y +30 ::: 9y+50

But we dont know the value of y hence Not sufficient

On combining both we can solve
4x-20/9x-50 = 4y/9y
we can solve to get the value of x

Hence Sufficient C
_________________
We must try to achieve the best within us


Thanks
Luckisnoexcuse
Manager
Manager
avatar
B
Joined: 13 Apr 2017
Posts: 82
Location: India
Concentration: General Management, International Business
GMAT 1: 660 Q40 V41
GPA: 3.4
WE: Engineering (Energy and Utilities)
Re: A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 21 Aug 2017, 00:21
Bunuel wrote:
A mixture consists of two spirits A and B; A evaporates at the rate of 2 ml per minute and B at 3 ml per minute. What will be the volume of the mixture after 10 minutes?

(1) Initial ratio of A and B in the mixture was 4 : 5.
(2) The final ratio of A and B in the mixture was 5 : 4.


Hi Bunuel

I am trying to solve this question using the allegation method. But I am messing up somewhere. Can you please explain how to solve it using the w1/w2=(A2-Aavg)/(Aavg-A1) (weighted average) method?

Thank you
Dkingdom
Manager
Manager
avatar
B
Joined: 07 Jun 2017
Posts: 100
Re: A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 21 Aug 2017, 00:54
We don't know the initial volume so how can we get the final volume?
Please explain, thank you
Current Student
User avatar
P
Joined: 18 Aug 2016
Posts: 619
Concentration: Strategy, Technology
GMAT 1: 630 Q47 V29
GMAT 2: 740 Q51 V38
GMAT ToolKit User Reviews Badge
Re: A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 21 Aug 2017, 01:18
2
2
pclawong wrote:
We don't know the initial volume so how can we get the final volume?
Please explain, thank you


Hi pclawong
we do not know the initial volume hence assumed it to be 9x
throuugh pre-evaporation we have two equations from (1) and (2)
4x-20 = 5y
5x-30 = 4y

4x-5y = 20
5x-4y = 30

20x - 25y = 100
20x - 16y = 120

9y = 20
y=20/9 and x= 70/9

hence pre-evaporation volume was 70 ml and post evaporation volume will be 20 ml
Let me know if it helped
_________________
We must try to achieve the best within us


Thanks
Luckisnoexcuse
Manager
Manager
avatar
B
Joined: 13 Apr 2017
Posts: 82
Location: India
Concentration: General Management, International Business
GMAT 1: 660 Q40 V41
GPA: 3.4
WE: Engineering (Energy and Utilities)
Re: A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 21 Aug 2017, 03:35
pclawong wrote:
We don't know the initial volume so how can we get the final volume?
Please explain, thank you


Alternatively you can use the following method:
We can solve this problem by equating the amounts of either A or B before and after evaporation.
CiVi = CfVf

As per the question, 20ml of A and 30ml of B have evaporated.

Lets solve for A.

(1)
Ci=4/9
(4/9) * x = Cf * (x-20)
We need to find x (total volume after 10 mins)
Since we do not have the value of Cf we cannot solve for x.
Insufficient

(2)
Cf=5/9
Ci * x = (5/9) * (x-20)
We need to find x (total volume after 10 mins)
Since we do not have the value of Ci we cannot solve for x.
Insufficient

(1) + (2)
Ci=4/9, Cf=5/9
(4/9) *x = (5/9) * (x-20)

Now we can solve for x

Ans : C

Hope it helps.
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 10553
Re: A mixture consists of two spirits A and B; A evaporates at the rate of  [#permalink]

Show Tags

New post 11 Apr 2019, 10:09
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.
_________________
GMAT Club Bot
Re: A mixture consists of two spirits A and B; A evaporates at the rate of   [#permalink] 11 Apr 2019, 10:09
Display posts from previous: Sort by

A mixture consists of two spirits A and B; A evaporates at the rate of

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.