It is currently 23 Sep 2017, 09:53

Happening Now:

Alleviate MBA app anxiety! Come to Chat Room #2


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

Events & Promotions in June
Open Detailed Calendar

M02-07

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

Hide Tags

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41698

Kudos [?]: 124614 [0], given: 12079

M02-07 [#permalink]

Show Tags

New post 16 Sep 2014, 00:17
Expert's post
22
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  95% (hard)

Question Stats:

54% (01:44) correct 46% (02:04) wrong based on 179 sessions

HideShow timer Statistics

Andy, George and Sally are a team of consultants working on Project Alpha. They have an eight hour deadline to complete the project. The team members work at constant rates throughout the eight hour period. If the team of three has to begin work now and no one else can work on this project, will Project Alpha be completed by the deadline?


(1) Sally can finish the project alone in \(4k+7\) hours, where \(k\) is a positive integer with a minimum value of 1 and a maximum value of 5.

(2) Working alone, George will take \(2k+1\) hours and Andy will take \(3+2k\) hours, where \(k\) is a positive integer with a minimum value of 1 and a maximum value of 5
[Reveal] Spoiler: OA

_________________

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

Kudos [?]: 124614 [0], given: 12079

Expert Post
2 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41698

Kudos [?]: 124614 [2], given: 12079

Re M02-07 [#permalink]

Show Tags

New post 16 Sep 2014, 00:17
2
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
Official Solution:


Statement (1) by itself is not sufficient. From S1, we know Sally can finish the project in \(4k+7\) hours, but we know nothing about George's or Andy's time. Check if Sally can finish the work by herself. If \(k\) is the smallest value (1), Sally will need 11 hours to finish the project. We need to know George's and/or Andy's rate.

Statement (2) by itself is sufficient. From S2, we know that George will take \(2k+1\) hours and Andy will take \(2k+3\) hours.

Check whether George and Andy can finish the project by themselves. Check to see if the maximum value of \(k\) is sufficient for these two together to finish the project. If the maximum value of \(k = 5\), then George needs 11 hours and Andy needs 13 hours to finish the project alone.

Working together for one hour, George and Andy will finish:
\(\frac{1}{11} + \frac{1}{13} = \frac{11+13}{11*13} = \frac{24}{143} \gt \frac{1}{8}\)

of the work. Thus, working together, George and Andy finish a greater portion of work per hour than the required \(\frac{1}{8}\). As a result, they will easily finish the project by themselves. It is not necessary to know Sally's time to answer the question.

Alternative explanation:

To complete the job on time, George and Andy have to complete \(\frac{1}{8}\) of the job each hour together or \(\frac{1}{16}\) each (50% of \(\frac{1}{8}\)). Because they complete \(\frac{1}{11}\) and \(\frac{1}{13}\) respectively, that's all we need to know.

Another method is to perform a rough calculation: \(\frac{1}{11}+\frac{1}{13} \approx \frac{1}{12}+\frac{1}{12}=\frac{2}{12}=\frac{1}{6} \gt \frac{1}{8}\).


Answer: B
_________________

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

Kudos [?]: 124614 [2], given: 12079

Intern
Intern
avatar
Joined: 23 Aug 2014
Posts: 42

Kudos [?]: 10 [0], given: 28

GMAT Date: 11-29-2014
Re: M02-07 [#permalink]

Show Tags

New post 13 Dec 2014, 00:05
Sorry, just 1 question. Lets say S2 gave a value more than 8 hours. Then it would be insufficient, but S1+S2 would be sufficient, right?

Kudos [?]: 10 [0], given: 28

Manager
Manager
avatar
Joined: 18 Sep 2014
Posts: 232

Kudos [?]: 44 [0], given: 5

Reviews Badge
Re: M02-07 [#permalink]

Show Tags

New post 23 Mar 2015, 05:46
Deeuk,

Firstly consider the below cases:

1. say, k =5 (Maximum)
Then also, on further simplification, 1/11 + 1/13 > 1/8

2. say, k =1 (Minimum)
Then also, on further simplification, 1/3 + 1/5 > 1/8

Both cases, its sufficient to decipher that both person sufficient to do alpha within the schedule of 8 hours. Hence B is the answer to the said question.

Yes, coming to your question, yes if we could find different solution to both cases, then we would have to consider the first option, then in that case, C would have been the answer.

Hope its clear.
_________________

Kindly press the Kudos to appreciate my post !! :-)

Kudos [?]: 44 [0], given: 5

Intern
Intern
avatar
Joined: 27 Sep 2015
Posts: 19

Kudos [?]: 1 [0], given: 9

WE: Sales (Transportation)
Re: M02-07 [#permalink]

Show Tags

New post 08 Feb 2016, 20:01
A really easy way to look at this is as follows:

for section (2) put 1 into the equation ( the minimum work value) for George and andy and you get G = 3 and A = 5. This add up to 8 so together they can complete it in 8 hours which is already enough to meet the deadline. therefore it doesn't even matter what Sallys rate is. Not sure if this is the correct rational but it worked for me.

Kudos [?]: 1 [0], given: 9

Expert Post
Math Forum Moderator
avatar
P
Joined: 02 Aug 2009
Posts: 4912

Kudos [?]: 5246 [0], given: 112

M02-07 [#permalink]

Show Tags

New post 08 Feb 2016, 20:42
mpcroaming wrote:
A really easy way to look at this is as follows:

for section (2) put 1 into the equation ( the minimum work value) for George and andy and you get G = 3 and A = 5. This add up to 8 so together they can complete it in 8 hours which is already enough to meet the deadline. therefore it doesn't even matter what Sallys rate is. Not sure if this is the correct rational but it worked for me.



hi,

your method is wrong on two counts..
George will take 2k+1 hours and Andy will take 3+2k hours,
1) firstly by substituting k as 1, you are taking the minimum time they will take.
so G alone can finish in 3 hrs, and he doesn't require anyone to finish before 8 hrs....
SO, you look at the max time they take to be certain that even at the lowest speed they can finish the work in <8 hrs..

2) second fault is if G can do it in 3 hrs and A can do in 5 hrs...
both combined will not do it in 3+5 hrs, but less than 3 hrs..
if some one alone was doing in 3 hrs, and he gets help, he will do it in lesser time..

Hope the concepts have become slightly clearer..
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 5246 [0], given: 112

Intern
Intern
avatar
S
Joined: 12 Mar 2015
Posts: 34

Kudos [?]: 8 [0], given: 165

Schools: Haas '20
GPA: 2.99
WE: Corporate Finance (Aerospace and Defense)
GMAT ToolKit User
Re: M02-07 [#permalink]

Show Tags

New post 03 May 2016, 06:54
chetan2u wrote:
mpcroaming wrote:
A really easy way to look at this is as follows:

for section (2) put 1 into the equation ( the minimum work value) for George and andy and you get G = 3 and A = 5. This add up to 8 so together they can complete it in 8 hours which is already enough to meet the deadline. therefore it doesn't even matter what Sallys rate is. Not sure if this is the correct rational but it worked for me.



hi,

your method is wrong on two counts..
George will take 2k+1 hours and Andy will take 3+2k hours,
1) firstly by substituting k as 1, you are taking the minimum time they will take.
so G alone can finish in 3 hrs, and he doesn't require anyone to finish before 8 hrs....
SO, you look at the max time they take to be certain that even at the lowest speed they can finish the work in <8 hrs..

2) second fault is if G can do it in 3 hrs and A can do in 5 hrs...
both combined will not do it in 3+5 hrs, but less than 3 hrs..
if some one alone was doing in 3 hrs, and he gets help, he will do it in lesser time..

Hope the concepts have become slightly clearer..



Thank you very much! Your explanation really helped me out.

Kudos [?]: 8 [0], given: 165

Manager
Manager
avatar
B
Joined: 28 Aug 2016
Posts: 86

Kudos [?]: 16 [0], given: 32

Concentration: Strategy, General Management
M02-07 [#permalink]

Show Tags

New post 29 Sep 2016, 05:45
For 2), I did it slightly differently although it is basically a same solution as the explanation.

Set k = 5 (maximum)

time = 8 hrs

So the equation to verify would be

8/11 + 8/13 > 1

Which it clearly is. Therefore 2) is sufficient. I think this way is much easier to tell at first glance without doing any further calculation rather than comparing fractions.

Kudos [?]: 16 [0], given: 32

Intern
Intern
avatar
Joined: 26 Jul 2016
Posts: 31

Kudos [?]: -18 [0], given: 10

Location: India
Concentration: Operations, Entrepreneurship
Schools: Tepper '19
GPA: 3.69
WE: Analyst (Manufacturing)
Re: M02-07 [#permalink]

Show Tags

New post 10 Oct 2016, 05:58
hi, why can't it be done in this way
George will take 2k+1 hours and Andy will take 3+2k hours
taking minimum value (1) 2(1) +1 & 3+2(1)= 3+8

wprk done in one hour = 1/3 +1/5
5/15+3/15=8/15 in one hour by this we can easily state that that work can be done in less than 8 hours.

Kudos [?]: -18 [0], given: 10

Manager
Manager
avatar
B
Joined: 11 Aug 2016
Posts: 60

Kudos [?]: 8 [0], given: 56

Location: India
Concentration: General Management, Finance
Schools: ISB '19, Rotman '19, IIM
GMAT 1: 550 Q36 V26
GMAT 2: 550 Q41 V25
GMAT 3: 570 Q44 V25
GPA: 3.6
WE: General Management (Other)
GMAT ToolKit User Reviews Badge
Re: M02-07 [#permalink]

Show Tags

New post 17 Aug 2017, 03:02
Very nice question.
All that has been asked is can the worked be finished on time.
And if even one can do it, then we won't require rest.

Kudos [?]: 8 [0], given: 56

Re: M02-07   [#permalink] 17 Aug 2017, 03:02
Display posts from previous: Sort by

M02-07

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

Moderators: Bunuel, Vyshak



GMAT Club MBA Forum Home| About| Terms and Conditions| 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®.