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

 It is currently 16 Jan 2019, 20:49

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

Events & Promotions

Events & Promotions in January
PrevNext
SuMoTuWeThFrSa
303112345
6789101112
13141516171819
20212223242526
272829303112
Open Detailed Calendar
• The winning strategy for a high GRE score

January 17, 2019

January 17, 2019

08:00 AM PST

09:00 AM PST

Learn the winning strategy for a high GRE score — what do people who reach a high score do differently? We're going to share insights, tips and strategies from data we've collected from over 50,000 students who used examPAL.
• Free GMAT Strategy Webinar

January 19, 2019

January 19, 2019

07:00 AM PST

09:00 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.

Working alone, R can complete a certain kind of job in 9 hours. R and

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

Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 52164
Working alone, R can complete a certain kind of job in 9 hours. R and  [#permalink]

Show Tags

17 Nov 2015, 23:18
00:00

Difficulty:

5% (low)

Question Stats:

85% (00:52) correct 15% (01:14) wrong based on 156 sessions

HideShow timer Statistics

Working alone, R can complete a certain kind of job in 9 hours. R and S, working together at their respective rates, can complete one of these jobs in 6 hours. In how many hours can S, working alone, complete one of these jobs?

(A) 18
(B) 12
(C) 9
(D) 6
(E) 3

Project PS Butler : Question #103

Subscribe to get Daily Email - Click Here | Subscribe via RSS - RSS

_________________
Director
Joined: 20 Feb 2015
Posts: 795
Concentration: Strategy, General Management
Re: Working alone, R can complete a certain kind of job in 9 hours. R and  [#permalink]

Show Tags

17 Nov 2015, 23:29
working together R and S can complete the job in 6 hours
which means
1/R + 1/S =1/6
R can complete the job in 9 hours
therefore, 1/9+1/S=1/6
or,1/S=1/6-1/9
1/S=1/18
Thus S working alone can complete the job in 18 hours
Verbal Forum Moderator
Status: Greatness begins beyond your comfort zone
Joined: 08 Dec 2013
Posts: 2166
Location: India
Concentration: General Management, Strategy
Schools: Kelley '20, ISB '19
GPA: 3.2
WE: Information Technology (Consulting)
Re: Working alone, R can complete a certain kind of job in 9 hours. R and  [#permalink]

Show Tags

17 Nov 2015, 23:32
Let total time taken by S to complete the job = S
total time taken by R to complete the job = 9
Work done by R in an hour
1/R = 1/9

Working together R and S can complete the job in 6 hours
1/R + 1/S = 1/6
=>1/S = 1/6 - 1/R
= 1/6 - 1/9
= 1/18
=> S = 18 hours

Answer A
_________________

When everything seems to be going against you, remember that the airplane takes off against the wind, not with it. - Henry Ford
The Moment You Think About Giving Up, Think Of The Reason Why You Held On So Long
+1 Kudos if you find this post helpful

EMPOWERgmat Instructor
Status: GMAT Assassin/Co-Founder
Affiliations: EMPOWERgmat
Joined: 19 Dec 2014
Posts: 13330
Location: United States (CA)
GMAT 1: 800 Q51 V49
GRE 1: Q170 V170
Re: Working alone, R can complete a certain kind of job in 9 hours. R and  [#permalink]

Show Tags

29 Nov 2015, 12:08
1
Hi All,

This question is a variation of a 'Work Formula' question (it involves 2 'entities' working on the same task together), so we can use the Work Formula to solve it.

Work = (A)(B)/(A+B) where A and B are the individual times that it takes the 2 entities to complete the task on their own.

Here, we're told that R can complete a job in 9 hours and that R and S (when working together) can complete a job in 6 hours. We're asked how long it takes S to complete the job alone.

The 'twist' here is that we have to 'work back' to find the value of S...

(9)(S)/(9 + S) = 6

9S = 54 + 6S
3S = 54
S = 18 hours

Final Answer:

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

760+: Learn What GMAT Assassins Do to Score at the Highest Levels
Contact Rich at: Rich.C@empowergmat.com

Rich Cohen

Co-Founder & GMAT Assassin

Special Offer: Save \$75 + GMAT Club Tests Free
Official GMAT Exam Packs + 70 Pt. Improvement Guarantee
www.empowergmat.com/

*****Select EMPOWERgmat Courses now include ALL 6 Official GMAC CATs!*****

Intern
Joined: 05 Oct 2017
Posts: 29
Location: India
Concentration: Finance, International Business
Schools: ISB '21, IIMA , IIMC
GPA: 4
WE: Analyst (Energy and Utilities)
Re: Working alone, R can complete a certain kind of job in 9 hours. R and  [#permalink]

Show Tags

27 Dec 2018, 10:34
Bunuel wrote:
Working alone, R can complete a certain kind of job in 9 hours. R and S, working together at their respective rates, can complete one of these jobs in 6 hours. In how many hours can S, working alone, complete one of these jobs?

(A) 18
(B) 12
(C) 9
(D) 6
(E) 3

Project PS Butler : Question #103

Subscribe to get Daily Email - Click Here | Subscribe via RSS - RSS

if r and s be the amount of work done by R and S in 1 hour respectively.

then r=1/9 & r+s = 1/6 so s= 1/6-1/9 = 1/18

hence ans A
GMAT Tutor
Joined: 07 Nov 2016
Posts: 45
GMAT 1: 760 Q51 V42
Re: Working alone, R can complete a certain kind of job in 9 hours. R and  [#permalink]

Show Tags

27 Dec 2018, 22:24
R alone : 9 hours

R and S together : 6 hours

S alone = ?

It can easily be seen that if S = 9, R and S = 4.5

Since R and S = 6, S is more than 9 i.e 12 or 18 from the answer choices

We know that time taken by R and S = $$\frac{(RS)}{(R+S)}$$,

If we substitute R = 9, and S = 12 in the above formula, We get $$\frac{(9*12)}{(9+12)}$$

By inspection this is not an integer

So, We are left with S= 18

Choice A
_________________

Please contact me at ksrutisagar@gmail.com

Re: Working alone, R can complete a certain kind of job in 9 hours. R and &nbs [#permalink] 27 Dec 2018, 22:24
Display posts from previous: Sort by

Working alone, R can complete a certain kind of job in 9 hours. R and

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

 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®.