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

It is currently 23 Oct 2018, 11:25

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

Working alone at its constant rate, pump x pumped out 1/3 of the water

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

Hide Tags

Intern
Intern
avatar
S
Joined: 12 Mar 2015
Posts: 45
Schools: Haas '20
GPA: 2.99
WE: Corporate Finance (Aerospace and Defense)
GMAT ToolKit User
Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 22 Jan 2017, 14:57
4
00:00
A
B
C
D
E

Difficulty:

  15% (low)

Question Stats:

85% (02:05) correct 15% (02:32) wrong based on 248 sessions

HideShow timer Statistics

Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.

A: 18
B: 24
C: 36
D: 48
E: 52
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Aug 2009
Posts: 6983
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 22 Jan 2017, 16:13
5
3
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.

A: 18
B: 24
C: 36
D: 48
E: 52


Hi

Three steps that will get you to answer..
1) time of pump x..
1/3 in 4 hrs, so complete in 4*3=12 hrs

2) combined time of x and y..
(1-1/3) or 2/3 in 6 hrs, so complete in 6*3/2=9 hrs..

3) finally our answer or pump y..
1/(combined time) - 1/(time of pump x)= 1/9-1/12=1/36..
So 36hrs

Hope it helps
_________________

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

General Discussion
Intern
Intern
avatar
S
Joined: 12 Mar 2015
Posts: 45
Schools: Haas '20
GPA: 2.99
WE: Corporate Finance (Aerospace and Defense)
GMAT ToolKit User
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 22 Jan 2017, 16:43
chetan2u wrote:
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.

A: 18
B: 24
C: 36
D: 48
E: 52


Hi

Three steps that will get you to answer..
1) time of pump x..
1/3 in 4 hrs, so complete in 4*3=12 hrs

2) combined time of x and y..
(1-1/3) or 2/3 in 6 hrs, so complete in 6*3/2=9 hrs..

3) finally our answer or pump y..
1/(combined time) - 1/(time of pump x)= 1/9-1/12=1/36..
So 36hrs

Hope it helps



Wow thank you so much!
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 50058
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 23 Jan 2017, 01:16
2
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.

A: 18
B: 24
C: 36
D: 48
E: 52


Very similar questions to practice:
working-at-constant-rate-pump-x-pumped-out-half-of-the-water-in-a-flo-223089.html
working-alone-at-its-constant-rate-pump-x-pumped-out-of-the-water-216023.html
_________________

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

Intern
Intern
avatar
S
Joined: 12 Mar 2015
Posts: 45
Schools: Haas '20
GPA: 2.99
WE: Corporate Finance (Aerospace and Defense)
GMAT ToolKit User
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 23 Jan 2017, 12:12
Bunuel wrote:
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.

A: 18
B: 24
C: 36
D: 48
E: 52


Very similar questions to practice:
working-at-constant-rate-pump-x-pumped-out-half-of-the-water-in-a-flo-223089.html
working-alone-at-its-constant-rate-pump-x-pumped-out-of-the-water-216023.html


Thank you Bunuel! You are such an amazing help!
VP
VP
avatar
P
Joined: 07 Dec 2014
Posts: 1104
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 23 Jan 2017, 12:40
1
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

A: 18
B: 24
C: 36
D: 48
E: 52

rate of x=1/12
rate of x and y=1/9
rate of y=1/9-1/12=1/36
36 hours
C
Target Test Prep Representative
User avatar
P
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 3906
Location: United States (CA)
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 25 Jan 2017, 10:16
2
3
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

A: 18
B: 24
C: 36
D: 48
E: 52


We are given that pump X pumped out 1/3 of the water in a pool in 4 hours. Since rate = work/time, the rate of pump X is (1/3)/4 = 1/12. Also, since 1/3 of the water was pumped out of the pool, 2/3 was left to be removed.

Since pump X and Y pumped out 2/3 of the water in 6 hours, the combined rate of pumps X and Y is (2/3)/6 = 2/18 = 1/9.

Finally, since rate of pump X + rate of pump Y = the combined rate of pumps X and Y, the rate of pump Y is:

1/9 - 1/12 = 4/36 - 3/36 = 1/36

Thus, pump Y can pump all the water out of the pool in 36 hours.

Answer: C
_________________

Scott Woodbury-Stewart
Founder and CEO

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

Manager
Manager
avatar
S
Joined: 13 Dec 2013
Posts: 155
Location: United States (NY)
Concentration: Nonprofit, International Business
GMAT 1: 710 Q46 V41
GMAT 2: 720 Q48 V40
GPA: 4
WE: Consulting (Consulting)
Reviews Badge
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 14 Apr 2017, 14:03
alandizzle wrote:
Working alone at its constant rate, pump x pumped out 1/3 of the water in a pool in 4 hours. Then pump Y started working and the two pumps, working simultaneously at their respective constant rates, pumped out the rest of the water in 6 hours. How many hours would it have taken pump Y, working alone at its constant rate, to pump out all the water that was pumped out of the pool?

I'm having a tough time with this question, can someone help me break it down? I guessed correctly but not sure how to get there within 2 minutes.

A: 18
B: 24
C: 36
D: 48
E: 52


1/X (amount of work done by X in 1h)= (1/3)/4=1/12
Now, there are 2/3 of work left to be done.
(1/X)+(1/Y)=(2/3)/6
(1/12)+(1/Y)=1/9
(1/Y)=(12/108)-(9/108)=3/108=1/36
Time = reciprocal of rate (work done in one hour) = 36h. C
Intern
Intern
avatar
B
Joined: 26 Jul 2017
Posts: 5
Location: Pakistan
Concentration: Strategy, Organizational Behavior
GPA: 2.25
WE: Consulting (Consulting)
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water  [#permalink]

Show Tags

New post 04 Sep 2018, 06:21
We can also use the percentage method to solve this question

we know that pump A did 1/3 of work in 4 hours, which means that 1/12 or 8.33% of work was done by pump A in one hour.

Now 2/3 or 66.6% of work is left. This work was done by pump A and B in 6 Hours. which means that 11.1% work was done in 1 hour. Of the 11.1% work 8.33% was done by A and 11.1 - 8.33 = 2.67% of work was done by Pump B.

If we round 2.67 to 3 It will take pump B 33.3 hours to do the work. The closest is 36 which is the answer.

Thanks
GMAT Club Bot
Re: Working alone at its constant rate, pump x pumped out 1/3 of the water &nbs [#permalink] 04 Sep 2018, 06:21
Display posts from previous: Sort by

Working alone at its constant rate, pump x pumped out 1/3 of the water

  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®.