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

It is currently 14 Nov 2018, 01:05

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 November
PrevNext
SuMoTuWeThFrSa
28293031123
45678910
11121314151617
18192021222324
2526272829301
Open Detailed Calendar
  • $450 Tuition Credit & Official CAT Packs FREE

     November 15, 2018

     November 15, 2018

     10:00 PM MST

     11:00 PM MST

    EMPOWERgmat is giving away the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299)
  • Free GMAT Strategy Webinar

     November 17, 2018

     November 17, 2018

     07:00 AM PST

     09:00 AM PST

    Nov. 17, 7 AM PST. Aiming to score 760+? Attend this FREE session to learn how to Define your GMAT Strategy, Create your Study Plan and Master the Core Skills to excel on the GMAT.

Three pipes A, B and C can fill a tank in 6 hours. After working at i

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

Hide Tags

Manager
Manager
User avatar
Joined: 04 Aug 2013
Posts: 96
Location: India
Schools: McCombs '17
GMAT 1: 670 Q47 V35
GPA: 3
WE: Manufacturing and Production (Pharmaceuticals and Biotech)
Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 10 Mar 2016, 18:31
1
12
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

73% (01:48) correct 27% (01:47) wrong based on 169 sessions

HideShow timer Statistics

Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. How many hours will take C alone to fill the tank ?

A. 10
B. 12
C. 14
D. 16
E. 18
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 7025
Re: Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 10 Mar 2016, 19:00
3
anceer wrote:
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. How many hours will take C alone to fill the tank ?

A. 10
B. 12
C. 14
D. 16
E. 18


Hi,

INFO


1) ONE hour work of all three is 1/6
2) after two hours, C is closed

INFERENCE


1) In 2 hours all three would do 2/6 of work =1/3 of work..
2) remaining 2/3 rd of work is done by all three in 4 hours and by ONLY a and B in 7 hrs..


SOLUTION..


therefore lets find how much time C will take to complete this--
one hour work- 1/4-1/7=3/28..
so C takes 28/3 hour to complete 2/3 work..
so C will complete the entire work in 28/3 * 3/2=14 days..
C

_________________

1) Absolute modulus : http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
2)Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html
3) effects of arithmetic operations : https://gmatclub.com/forum/effects-of-arithmetic-operations-on-fractions-269413.html


GMAT online Tutor

Manager
Manager
avatar
B
Joined: 03 May 2014
Posts: 161
Location: India
WE: Sales (Mutual Funds and Brokerage)
Re: Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 02 Apr 2016, 23:20
2
Combined rate of work
1/a+1/b+1/c=1/6
Work done by 3 in 2 hrs=2x1/6=1/3
Work left to be done
1-1/3=2/3.
This work is done by b&c in 7 hrs.
Thus Rate of work is
Work/time=2/3/7=2/21
Therefore
1/a-2/21=1/6. Solve the equation a=14 hrs

Posted from my mobile device
Board of Directors
User avatar
P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4207
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User Premium Member
Re: Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 03 Apr 2016, 03:52
3
1
anceer wrote:
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. How many hours will take C alone to fill the tank ?


Let the total capacity of the tank be 42 units (LCM of 2,6 & 7)

anceer wrote:
Three pipes A, B and C can fill a tank in 6 hours.


Efficiency of ABC is 42/7 = 6units/hr

anceer wrote:
After working at it together for 2 hours,


In 2 hours A B and C fill up 14 units of the tank , thus 28 units are left.

anceer wrote:
C is closed and A and B can fill the remaining part in 7 hours. How many hours will take C alone to fill the tank ?


A and B fill up 28 units in 7 hours thus efficiency of A & B is 4 units

We know , A+B+C = 7 and A + B = 4

So, Efficiency of C is 3 units/hr

Thus the time required to fill up the entire tank is 42/3 = 14 hours.
_________________

Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )

Board of Directors
User avatar
P
Joined: 17 Jul 2014
Posts: 2645
Location: United States (IL)
Concentration: Finance, Economics
GMAT 1: 650 Q49 V30
GPA: 3.92
WE: General Management (Transportation)
GMAT ToolKit User Premium Member Reviews Badge
Re: Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 16 Sep 2016, 06:56
2
i solved this way...
total work to be done = 6 parts.
all together can do 1 part in 1 hour.
2 hours passed - 2 parts were done. so left 4 parts to finish.
4 parts out of total 6 parts is 2/3.
now..A and B finish filling 2/3 in 7 hours. 2/3 divide by 7 = 2/21. this is the rate for A and B.
to find the rate for C, subtract from 1/6 (rate of all three pipes) the rate of A and B (2/21)
1/6 - 2/21 (multiply first fraction by 7, second by 2) = 7/42 - 4/42 = 3/42
now 3/42 is the rate of C. it can fill 3 pools in 42 hours, or one in 14 hours.
answer is C.
Senior SC Moderator
avatar
V
Joined: 22 May 2016
Posts: 2092
Premium Member CAT Tests
Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 15 Oct 2017, 16:03
1
anceer wrote:
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. How many hours will take C alone to fill the tank ?

A. 10
B. 12
C. 14
D. 16
E. 18

1) Combined rate: A, B, and C fill one tank in six hours:

\(\frac{1}{A} +
\frac{1}{B} +
\frac{1}{C} = \frac{1}{6}\)

2) Amt of work finished, work remaining. They work at that rate for 2 hours. \(r*t = W\)

They finish:\((\frac{1}{6}* 2) = \frac{2}{6}= \frac{1}{3}\) tank

Remaining work: \((1 - \frac{1}{3})= \frac{2}{3}\) tank

3) Rate of A and B? C stops. A and B do remaining \(\frac{2}{3}\) in 7 hrs

A and B's combined rate? \(W/t = r\)

\(\frac{(\frac{2}{3})}{7}\) = \(\frac{2}{21}\)

That is, \(\frac{1}{A} +
\frac{1}{B} =
\frac{2}{21}\)

4) Find C's rate. Numbers aren't as bad as they look.

\(\frac{1}{A} +
\frac{1}{B} +
\frac{1}{C} = \frac{1}{6}\)

\(\frac{2}{21} +
\frac{1}{C} = \frac{1}{6}\)

Multiply each term by (6 * 21) = 126

\(12 + \frac{126}{C} = 21\)

\(\frac{126}{C} = 9\)

\(\frac{1}{C} = \frac{9}{126}=\) C's rate

5) C's time?
When work is 1, flip rate to get time. C's time: \(\frac{126}{9}\) = 14 hours

OR \((\frac{W}{r} = t)\):

\(\frac{1}{(\frac{9}{126})}\)

\(\frac{126}{9}
= 14\) hours

Answer C
Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8527
Location: Pune, India
Re: Three pipes A, B and C can fill a tank in 6 hours. After working at i  [#permalink]

Show Tags

New post 11 Nov 2018, 22:57
anceer wrote:
Three pipes A, B and C can fill a tank in 6 hours. After working at it together for 2 hours, C is closed and A and B can fill the remaining part in 7 hours. How many hours will take C alone to fill the tank ?

A. 10
B. 12
C. 14
D. 16
E. 18


A, B and C fill the tank in 6 hrs so their combined rate is 1/6 tank/hr
In 2 hrs, they will fill 1/3rd of the tank.

Now leftover 2/3rd of the tank is filled by A and B in 7 hrs. So combined rate of A and B = (2/3)/7 = 2/21 tank/hr

Rates are additive so,
Rate of C = Rate of A,B and C - Rate of A and B = 1/6 - 2/21 = 3/42 = 1/14
Hence, C alone will fill 1 tank in 14 hrs.

Answer (C)
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

GMAT Club Bot
Re: Three pipes A, B and C can fill a tank in 6 hours. After working at i &nbs [#permalink] 11 Nov 2018, 22:57
Display posts from previous: Sort by

Three pipes A, B and C can fill a tank in 6 hours. After working at i

  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®.