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

It is currently 18 Feb 2019, 14:44

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
Events & Promotions in February
PrevNext
SuMoTuWeThFrSa
272829303112
3456789
10111213141516
17181920212223
242526272812
Open Detailed Calendar
  • Valentine's day SALE is on! 25% off.

     February 18, 2019

     February 18, 2019

     10:00 PM PST

     11:00 PM PST

    We don’t care what your relationship status this year - we love you just the way you are. AND we want you to crush the GMAT!
  • Get FREE Daily Quiz for 2 months

     February 18, 2019

     February 18, 2019

     10:00 PM PST

     11:00 PM PST

    Buy "All-In-One Standard ($149)", get free Daily quiz (2 mon). Coupon code : SPECIAL

A tank has both an inlet pipe and an outlet pipe. Working

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

Hide Tags

 
Senior Manager
Senior Manager
avatar
Joined: 10 Apr 2012
Posts: 268
Location: United States
Concentration: Technology, Other
GPA: 2.44
WE: Project Management (Telecommunications)
GMAT ToolKit User Premium Member
A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post Updated on: 21 Jan 2014, 03:21
3
36
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

75% (02:36) correct 25% (02:51) wrong based on 356 sessions

HideShow timer Statistics

A tank has both an inlet pipe and an outlet pipe. Working alone, the inlet pipe can fill up the tank in 5 hours. Working alone, the outlet pipe can empty out the tank in 15 hours. If it is desired that the tank should be filled, from empty, exactly 6 hours after the inlet pipe is turned on at 9:30am, then at what time should the outlet pipe be opened ?

A. 10:00am
B. 10:45am
C. 12:00pm
D. 12:30pm
E. 1:30pm

Originally posted by guerrero25 on 20 Jan 2014, 07:24.
Last edited by guerrero25 on 21 Jan 2014, 03:21, edited 1 time in total.
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 52938
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 20 Jan 2014, 07:47
10
8
guerrero25 wrote:
A tank has both an inlet pipe and an outlet pipe. Working alone, the inlet pipe can fill up the tank in 5 hours. Working alone, the outlet pipe can empty out the tank in 15 hours. If it is desired that the tank should be filled, from empty, exactly 6 hours after the inlet pipe is turned on at 9:30am, then at what time should the outlet pipe be opened ?

A) 10:00am

B) 10:45am

C) 12:00pm

D) 12:30pm

E) 1:30pm


I do not have the OA with me right now .


In 6 hours the inlet pipe will pump in water equal to 6*1/5 = 6/5 of the pool. So, 1/5 more than necessary, which should be compensated by the outlet pipe. To pump out 1/5 of the water the outlet pipe needs 15/5 = 3 hours.

Therefore, the outlet pipe should be opened at 9:30am + 6 hours - 3 hours = 12:30pm.

Answer: D.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

General Discussion
Manager
Manager
avatar
B
Joined: 31 Mar 2013
Posts: 64
Location: India
GPA: 3.02
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 20 Jan 2014, 22:05
Bunuel wrote:
guerrero25 wrote:
A tank has both an inlet pipe and an outlet pipe. Working alone, the inlet pipe can fill up the tank in 5 hours. Working alone, the outlet pipe can empty out the tank in 15 hours. If it is desired that the tank should be filled, from empty, exactly 6 hours after the inlet pipe is turned on at 9:30am, then at what time should the outlet pipe be opened ?

A) 10:00am

B) 10:45am

C) 12:00pm

D) 12:30pm

E) 1:30pm


I do not have the OA with me right now .


In 6 hours the inlet pipe will pump in water equal to 6*1/5 = 6/5 of the pool. So, 1/5 more than necessary, which should be compensated by the outlet pipe. To pump out 1/5 of the water the outlet pipe needs 15/5 = 3 hours.

Therefore, the outlet pipe should be opened at 9:30am + 6 hours - 3 hours = 12:30pm.

Answer: D.


Bunuel, but to pump out the excess 1/5 of water, should we not use the combined rate (inflow+outflow)? The combined rate would be 10l outflow/hour. So time required will be 10/5 = 2 hours.

Therefore, the outlet pipe should be opened at 9:30am + 6 hours - 2 hours = 1:30pm. Any mistake here?
Director
Director
User avatar
S
Affiliations: CrackVerbal
Joined: 03 Oct 2013
Posts: 532
Location: India
GMAT 1: 780 Q51 V46
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 20 Jan 2014, 22:45
1
Let us say that the capacity of the tank is 30 liters

Inlet --- 6 liters per hour
Outlet - 2 liters per hour

Let us say it should be turned on after x hours. Total time taken to fill 6 hours

6x + (4)(6-x) = 30
6x + 24 - 4x = 30
2x = 6
x = 3
So it should be opened after 3 hours i.e. 12:30 am
_________________

For more info on GMAT and MBA, follow us on @AskCrackVerbal

Register for the Free GMAT Video Training Course : https://crackverbal.com/MBA-Through-GMAT-2019-Registration

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 52938
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 21 Jan 2014, 01:43
HKHR wrote:
Bunuel wrote:
guerrero25 wrote:
A tank has both an inlet pipe and an outlet pipe. Working alone, the inlet pipe can fill up the tank in 5 hours. Working alone, the outlet pipe can empty out the tank in 15 hours. If it is desired that the tank should be filled, from empty, exactly 6 hours after the inlet pipe is turned on at 9:30am, then at what time should the outlet pipe be opened ?

A) 10:00am

B) 10:45am

C) 12:00pm

D) 12:30pm

E) 1:30pm


I do not have the OA with me right now .


In 6 hours the inlet pipe will pump in water equal to 6*1/5 = 6/5 of the pool. So, 1/5 more than necessary, which should be compensated by the outlet pipe. To pump out 1/5 of the water the outlet pipe needs 15/5 = 3 hours.

Therefore, the outlet pipe should be opened at 9:30am + 6 hours - 3 hours = 12:30pm.

Answer: D.


Bunuel, but to pump out the excess 1/5 of water, should we not use the combined rate (inflow+outflow)? The combined rate would be 10l outflow/hour. So time required will be 10/5 = 2 hours.

Therefore, the outlet pipe should be opened at 9:30am + 6 hours - 2 hours = 1:30pm. Any mistake here?


Not sure how you got the numbers there. Combined rate is INFLOW of 1/5-1/15=2/15 pool/hour...

We are interested on time needed for outlet pipe to compensate the excess of 1/5 of the pool.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Director
Director
User avatar
G
Joined: 23 Jan 2013
Posts: 557
Schools: Cambridge'16
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 26 Sep 2014, 21:44
1
1
Inlet: 1/5 t/h
Oulet: 1/15 t/h
together working 1/5-1/15=2/15 t/h

2/15*6=12/15 filled, so 3/15 unfilled

3/15:1/15=3 hours of outlet should subtract. 6-3=3 hours

Answer: D
Manager
Manager
User avatar
Joined: 12 Jan 2015
Posts: 198
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 30 May 2016, 12:14
Hi chetan2u,

I am able to get the solution from the following method-
1/5 * t + 2/15 * (6-t) = 1 (Since the tank should be full after 6 hours)
t/5 + 12/15 -2t/15 = 1
12/15 + t/15 = 1
t/15 = 3/15
t=3

However, I want to discuss 1 more approach
Inlet pipe rate= 1/5
outlet pipe rate= 1/15
Combined rate of Inlet and Outlet = 1/5 - 1/15 = 2/15

As, mentioned in the question the tank gets filled in 6 hours.
We can say that Inlet pipe works for 6 hours and
and Inlet = outlet pipe works for x hours

So, I tried to make the equation as

(1/5)*6 + (2/15)*x= What do I need to put on RHS

Can you please assist.

Thanks and Regards,
Prakhar
_________________

Thanks and Regards,
Prakhar

Retired Moderator
User avatar
S
Joined: 18 Sep 2014
Posts: 1111
Location: India
GMAT ToolKit User Premium Member Reviews Badge
A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 17 Sep 2016, 23:01
PrakharGMAT wrote:
Hi chetan2u,

I am able to get the solution from the following method-
1/5 * t + 2/15 * (6-t) = 1 (Since the tank should be full after 6 hours)
t/5 + 12/15 -2t/15 = 1
12/15 + t/15 = 1
t/15 = 3/15
t=3

However, I want to discuss 1 more approach
Inlet pipe rate= 1/5
outlet pipe rate= 1/15
Combined rate of Inlet and Outlet = 1/5 - 1/15 = 2/15

As, mentioned in the question the tank gets filled in 6 hours.
We can say that Inlet pipe works for 6 hours and
and Inlet = outlet pipe works for x hours

So, I tried to make the equation as

(1/5)*6 + (2/15)*x= What do I need to put on RHS

Can you please assist.

Thanks and Regards,
Prakhar

PrakharGMAT

when you say 2/15 it means the combined work of both inlet and outlet. then you cannot consider 1/5 work of inlet for 6 hours since it will overlap with the combined time.

then equation will \(\frac{2}{15}x+\frac{1}{5}(6-x)=1\)(Since the tank should be full after 68 hours)
solving this equation will result \(x=3\).
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9843
Premium Member
Re: A tank has both an inlet pipe and an outlet pipe. Working  [#permalink]

Show Tags

New post 06 Oct 2018, 08:19
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 Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

GMAT Club Bot
Re: A tank has both an inlet pipe and an outlet pipe. Working   [#permalink] 06 Oct 2018, 08:19
Display posts from previous: Sort by

A tank has both an inlet pipe and an outlet pipe. Working

  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®.