Find all School-related info fast with the new School-Specific MBA Forum

It is currently 25 May 2015, 19:44

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Machine M, working alone at its constant rate, produces x wi

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
2 KUDOS received
Intern
Intern
avatar
Joined: 24 Jan 2012
Posts: 10
Followers: 0

Kudos [?]: 56 [2] , given: 3

Machine M, working alone at its constant rate, produces x wi [#permalink] New post 24 Sep 2013, 07:29
2
This post received
KUDOS
6
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  65% (hard)

Question Stats:

55% (02:28) correct 45% (01:23) wrong based on 318 sessions
Machine M, working alone at its constant rate, produces x widgets every 4 minutes. Machine N, working alone at its constant rate, produces y widgets every 5 minutes. If machines M and N working simultaneously at their respective constant rates for 20 minutes, does machine M produce more widgets than machine N in that time ?

1) x > 0.8y
2) y = x + 1

My question :

1st statement tells that x/y < 4/5 => this means x's rate is more than y hence its sufficient to answer that machine M produce more widgets than machine N in that time

2nd statement says that y = x + 1
so if x = 2 widgets
then y = 3 widgets
this means that in 20 minutes x will produce 10 widgets and in same time y will produce 12 widgets so we get a definite answer hence its sufficient

Thats why I chose D but the OA is A

Can someone please explain ?
[Reveal] Spoiler: OA
Intern
Intern
avatar
Joined: 07 Aug 2013
Posts: 30
Followers: 0

Kudos [?]: 4 [0], given: 1

Re: Machine M and Machine N [#permalink] New post 24 Sep 2013, 07:46
The easiest way to look at the question (imo) is to say that;

Total produced= 20*(X/4)+20*(X/5) => T=5X+4Y

1) If x>0.8y

then T=5*(4y/5)+4Y => T=4y+4y since x is bigger then 0.8y T=(a number higher then 4)y +4y

Sufficient

2) y= x+1

then T=5X+4X+4 => Total M=5X Total N= 4x+4, if x=1 then no if x=1000 then yes

Insufficient
Expert Post
10 KUDOS received
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 27494
Followers: 4312

Kudos [?]: 42311 [10] , given: 6012

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 25 Sep 2013, 01:40
10
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
Machine M, working alone at its constant rate, produces x widgets every 4 minutes. Machine N, working alone at its constant rate, produces y widgets every 5 minutes. If machines M and N working simultaneously at their respective constant rates for 20 minutes, does machine M produce more widgets than machine N in that time ?

The rate of M = x/4 widgets per minute.
The rate of N = y/5 widgets per minute.

The question basically asks whether x/4 > y/5 (if per minute M produces more widgets than N, then M obviously produces more widgets than N, in 20, 30, ... or in any time period. So, we can compare the rates per 1 minute).


(1) x > 0.8y --> x > 4/5*y --> x/4 > y/5. Sufficient.

(2) y = x + 1. The question becomes: is x/4 > (x+1)/5, or is x>4. We don't know that. Not sufficient.

Answer: A.

Hope it's clear.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Manager
Manager
User avatar
Joined: 14 Jan 2013
Posts: 156
Concentration: Strategy, Technology
GMAT Date: 08-01-2013
GPA: 3.7
WE: Consulting (Consulting)
Followers: 2

Kudos [?]: 94 [0], given: 29

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 03 Mar 2014, 00:40
Bunuel wrote:
Machine M, working alone at its constant rate, produces x widgets every 4 minutes. Machine N, working alone at its constant rate, produces y widgets every 5 minutes. If machines M and N working simultaneously at their respective constant rates for 20 minutes, does machine M produce more widgets than machine N in that time ?

The rate of M = x/4 widgets per minute.
The rate of N = y/5 widgets per minute.

The question basically asks whether x/4 > y/5 (if per minute M produces more widgets than N, then M obviously produces more widgets than N, in 20, 30, ... or in any time period. So, we can compare the rates per 1 minute).


(1) x > 0.8y --> x > 4/5*y --> x/4 > y/5. Sufficient.

(2) y = x + 1. The question becomes: is x/4 > (x+1)/5, or is x>4. We don't know that. Not sufficient.

Answer: A.

Hope it's clear.



Bunuel,

I am not able to understand statement B. Can you please elaborate...
_________________

"Where are my Kudos" ............ Good Question = kudos

"Start enjoying all phases" & all Sections

__________________________________________________________________
http://gmatclub.com/forum/collection-of-articles-on-critical-reasoning-159959.html

percentages-700-800-level-questions-130588.html

700-to-800-level-quant-question-with-detail-soluition-143321.html

Expert Post
Math Expert
User avatar
Joined: 02 Sep 2009
Posts: 27494
Followers: 4312

Kudos [?]: 42311 [0], given: 6012

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 03 Mar 2014, 00:43
Expert's post
1
This post was
BOOKMARKED
Mountain14 wrote:
Bunuel wrote:
Machine M, working alone at its constant rate, produces x widgets every 4 minutes. Machine N, working alone at its constant rate, produces y widgets every 5 minutes. If machines M and N working simultaneously at their respective constant rates for 20 minutes, does machine M produce more widgets than machine N in that time ?

The rate of M = x/4 widgets per minute.
The rate of N = y/5 widgets per minute.

The question basically asks whether x/4 > y/5 (if per minute M produces more widgets than N, then M obviously produces more widgets than N, in 20, 30, ... or in any time period. So, we can compare the rates per 1 minute).


(1) x > 0.8y --> x > 4/5*y --> x/4 > y/5. Sufficient.

(2) y = x + 1. The question becomes: is x/4 > (x+1)/5, or is x>4. We don't know that. Not sufficient.

Answer: A.

Hope it's clear.



Bunuel,

I am not able to understand statement B. Can you please elaborate...


The question asks: is x/4 > y/5 ?

(2) says: y = x + 1. Substitute y = x + 1 into the question: is x/4 > (x+1)/5? --> is x > 4? Since we cannot answer this question, then this statement is not sufficient.

Hope it's clear.
_________________

NEW TO MATH FORUM? PLEASE READ THIS: ALL YOU NEED FOR QUANT!!!

PLEASE READ AND FOLLOW: 11 Rules for Posting!!!

RESOURCES: [GMAT MATH BOOK]; 1. Triangles; 2. Polygons; 3. Coordinate Geometry; 4. Factorials; 5. Circles; 6. Number Theory; 7. Remainders; 8. Overlapping Sets; 9. PDF of Math Book; 10. Remainders; 11. GMAT Prep Software Analysis NEW!!!; 12. SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) NEW!!!; 12. Tricky questions from previous years. NEW!!!;

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?
25 extra-hard Quant Tests

GMAT Club Premium Membership - big benefits and savings

Expert Post
Moderator
Moderator
User avatar
Joined: 20 Dec 2013
Posts: 184
Location: United States
GMAT 1: 640 Q44 V34
GMAT 2: 710 Q48 V40
GMAT 3: 720 Q49 V40
GPA: 3.16
WE: Consulting (Consumer Products)
Followers: 2

Kudos [?]: 44 [0], given: 71

GMAT ToolKit User Premium Member Reviews Badge CAT Tests
Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 03 Mar 2014, 20:26
Expert's post
M = x/4
N = y/5

5x/20>4y/20 -->
5x>4y?

I.
x>.8y
x>4y/5
5x>4y
Suff

II.
y=x+1
5x>4x+4 ?

x=1/20
1/4 > 1/5 + 4 --> no
x=5
25>24 --> yes

Insuff

A
_________________

MY GMAT BLOG - ADVICE - OPINIONS - ANALYSIS

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 4936
Followers: 297

Kudos [?]: 54 [0], given: 0

Premium Member
Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 28 Mar 2015, 11:17
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

Expert Post
EMPOWERgmat Instructor
User avatar
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 2187
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 94

Kudos [?]: 590 [0], given: 41

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 29 Mar 2015, 17:50
Expert's post
Hi All,

The way that you choose to organize your notes can often impact how much work you have to do to answer a given GMAT question (as well as the difficulty of the work). As such, part of your practice should really involve proper note-taking and working on the most 'efficient' ways for you to take notes, 'set up' your work, etc.

Here, we're told about the rates of 2 machines:
Machine M can produce X widgets in 4 minutes
Machine N can produce Y widgets in 5 minutes

We're then told that each machine works for 20 minutes. We're asked if Machine M produces more widgets than Machine N during that time.

During those 20 minutes, Machine M will produce 5X widgets and Machine N will produce 4Y widgets. In real simple terms, the question asks "is 5X > 4Y?" This is a YES/NO question. A mix of TESTing VALUES and Algebra will help to answer this question.

Fact 1: X > 0.8Y

We can multiply both sides of this inequality by 10....

10X > 8Y

Then divide both sides by 2...

5X > 4Y

Notice how the question asked "is 5X > 4Y?".... Fact 1 tells us that 5X IS greater than 4Y.
Fact 1 is SUFFICIENT

Fact 2: Y = X + 1

IF....
X = 1
Y = 2
5(1) is NOT > 4(2) and the answer to the question is NO.

IF...
X = 10
Y = 11
5(10) IS > 4(11) and the answer to the question is YES.
Fact 2 is INSUFFICIENT

Final Answer:
[Reveal] Spoiler:
A


GMAT assassins aren't born, they're made,
Rich
_________________

Rich Cohen
Rich.C@empowergmat.com
http://www.empowergmat.com

EMPOWERgmat GMAT Club Page, Study Plans, & Discounts
http://gmatclub.com/blog/courses/empowergmat-discount/?fl=menu

Image

1 KUDOS received
Intern
Intern
avatar
Joined: 08 Oct 2013
Posts: 18
Followers: 0

Kudos [?]: 9 [1] , given: 10

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 05 May 2015, 09:39
1
This post received
KUDOS
IMHO, this is a fairly easy question but the language will deceive you and you will mark the wrong answer unless you muscle the algebra. I solved by intuition and got it wrong.

So basically the question is, "Is the work done by Machine M is greater than the work done by N" (in 20 min)

Machine M: T= 4 min, W=x hence rate = x/4
Machine N: T= 5 min, W=y hence Rate = y/5

M will do more work if its rate is more than N so is x/4 > y/5?
x > 4/5(y) or is x > 0.8(y) ? - this is the Question

Statement 1 is a direct answer

Statement 2 becomes:
x/4 > y/5?
x/4 > (x+1)/5?
x/4 > (x+1)/4+1? - this is a general property of ratios. the inequality is true if x<4. Since we don't know the value of x, state2 is insufficient.

Answer A
Expert Post
1 KUDOS received
EMPOWERgmat Instructor
User avatar
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 2187
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: 340 Q170 V170
Followers: 94

Kudos [?]: 590 [1] , given: 41

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 06 May 2015, 10:31
1
This post received
KUDOS
Expert's post
Hi AjChakravarthy,

You bring up a number of important points in your post that are worth emphasizing:

1) Many DS questions ARE actually pretty easy, so you shouldn't take any chances when it comes to solving them - do the necessary work and get those points!

2) A Test Taker's "instinct" when dealing with DS question can often be incorrect, so you have to do enough work to PROVE that your instinct is correct.

3) Taking the time to "rewrite" the question can often lead to shortcuts later on in the work.

GMAT assassins aren't born, they're made,
Rich
_________________

Rich Cohen
Rich.C@empowergmat.com
http://www.empowergmat.com

EMPOWERgmat GMAT Club Page, Study Plans, & Discounts
http://gmatclub.com/blog/courses/empowergmat-discount/?fl=menu

Image

Intern
Intern
avatar
Joined: 08 Oct 2013
Posts: 18
Followers: 0

Kudos [?]: 9 [0], given: 10

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 06 May 2015, 11:08
EMPOWERgmatRichC wrote:
Hi AjChakravarthy,

You bring up a number of important points in your post that are worth emphasizing:

1) Many DS questions ARE actually pretty easy, so you shouldn't take any chances when it comes to solving them - do the necessary work and get those points!

2) A Test Taker's "instinct" when dealing with DS question can often be incorrect, so you have to do enough work to PROVE that your instinct is correct.

3) Taking the time to "rewrite" the question can often lead to shortcuts later on in the work.

GMAT assassins aren't born, they're made,
Rich


GMAT assassins aren't born, they're made, - very powerful.

Training to be one :)
Expert Post
Veritas Prep GMAT Instructor
User avatar
Joined: 16 Oct 2010
Posts: 5550
Location: Pune, India
Followers: 1372

Kudos [?]: 6981 [0], given: 178

Re: Machine M, working alone at its constant rate, produces x wi [#permalink] New post 06 May 2015, 19:45
Expert's post
violetsplash wrote:
Machine M, working alone at its constant rate, produces x widgets every 4 minutes. Machine N, working alone at its constant rate, produces y widgets every 5 minutes. If machines M and N working simultaneously at their respective constant rates for 20 minutes, does machine M produce more widgets than machine N in that time ?

1) x > 0.8y
2) y = x + 1

My question :

1st statement tells that x/y < 4/5 => this means x's rate is more than y hence its sufficient to answer that machine M produce more widgets than machine N in that time

2nd statement says that y = x + 1
so if x = 2 widgets
then y = 3 widgets
this means that in 20 minutes x will produce 10 widgets and in same time y will produce 12 widgets so we get a definite answer hence its sufficient

Thats why I chose D but the OA is A

Can someone please explain ?


Instead of picking numbers on this question, one might try to sit back and work out the logic of statement 2. It is quite simple once you get down to it.

You want to know whether x/4 > y/5. (x and y are good positive integers so no complications.)
So if x is greater than y, certainly x/4 will be greater than y/5 because x is divided by a smaller number.
If x is smaller than y, then it depends on how much smaller. If x is only slightly smaller than y, then it is possible that x/4 > y/5.

2nd statement says that y = x + 1
So x is 1 smaller than y. Now the problem is that you don't know the values of x and y so you don't know whether this 1 is huge in comparison to x and y or little. Therefore, you cannot say whether x/4 will be smaller or y/5.
_________________

Karishma
Veritas Prep | GMAT Instructor
My Blog

Get started with Veritas Prep GMAT On Demand for $199

Veritas Prep Reviews

Re: Machine M, working alone at its constant rate, produces x wi   [#permalink] 06 May 2015, 19:45
    Similar topics Author Replies Last post
Similar
Topics:
8 Experts publish their posts in the topic Machine M and Machine N working alone at their constant rate Reni 4 26 Jul 2014, 09:07
18 Experts publish their posts in the topic A newer machine, working alone at its constant rate gmacforjyoab 14 26 Oct 2013, 13:42
Working alone at its own constant rate, a machine seals k $uckafr33 4 02 Oct 2006, 10:39
Working alone at its own constant rate, a machine seals k acfuture 4 28 May 2006, 18:52
Working alone at it's own constant rate, a machine seals K ellisje22 2 03 Jan 2006, 17:45
Display posts from previous: Sort by

Machine M, working alone at its constant rate, produces x wi

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.