It is currently 21 Oct 2017, 05:32

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

Working at a constant rate, Sam can finish a job in 3 hours. Mark, als

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

Hide Tags

Expert Post
3 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41893

Kudos [?]: 129093 [3], given: 12194

Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 03 Jan 2016, 12:46
3
This post received
KUDOS
Expert's post
2
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  35% (medium)

Question Stats:

71% (01:23) correct 29% (01:40) wrong based on 143 sessions

HideShow timer Statistics

Working at a constant rate, Sam can finish a job in 3 hours. Mark, also working at a constant rate, can finish the same job in 12 hours. If they work together for 2 hours, how many minutes will it take Sam to finish the job, working alone at his constant rate?

A. 5
B. 20
C. 30
D. 60
E. 120
[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 [?]: 129093 [3], given: 12194

2 KUDOS received
Senior Manager
Senior Manager
avatar
Joined: 20 Feb 2015
Posts: 388

Kudos [?]: 100 [2], given: 10

Concentration: Strategy, General Management
Re: Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 06 Jan 2016, 02:53
2
This post received
KUDOS
in an hour sam can do 1/3 and for mark it is 1/12
sam's efficiency =100/3=33.33
mark's efficiency = 100/12=8.33
in two hours they completed = 83.32% of the work
work remaining = 16.68 %
time take by sam in minutes = (16.68/33.33)*60 =30.027 = ~30 minutes

Kudos [?]: 100 [2], given: 10

Expert Post
1 KUDOS received
Senior Manager
Senior Manager
User avatar
Joined: 20 Aug 2015
Posts: 396

Kudos [?]: 336 [1], given: 10

Location: India
GMAT 1: 760 Q50 V44
Re: Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 07 Jan 2016, 02:26
1
This post received
KUDOS
Expert's post
1
This post was
BOOKMARKED
Bunuel wrote:
Working at a constant rate, Sam can finish a job in 3 hours. Mark, also working at a constant rate, can finish the same job in 12 hours. If they work together for 2 hours, how many minutes will it take Sam to finish the job, working alone at his constant rate?

A. 5
B. 20
C. 30
D. 60
E. 120


Always assume the total work to be the LCM of the time given. This makes the calculations easier.

Assume the total work = 12 units.
Sam's rate of work = 12/3 = 4 units/hour
Mark's rate of work = 12/12 = 1 units/hour

Work completed by Sam and Mark together in 2 hours = 2(4 + 1) = 10 units.

Remaining work = 2 units.
Time taken by Sam in minutes = 2/4*60 = 30 minutes
Option C
_________________

Reach out to us at bondwithus@gmatify.com

Image

Kudos [?]: 336 [1], given: 10

Intern
Intern
User avatar
Joined: 11 Jan 2014
Posts: 31

Kudos [?]: 13 [0], given: 58

Location: Viet Nam
Concentration: Accounting, Finance
GPA: 3.17
WE: Analyst (Accounting)
Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 07 Jan 2016, 02:57
My answer is C.
Sol: Work = Rate x Hour
We have this table:
Hour-----Rate-----Work
Sam 3 1/3 1
Mark 12 1/12 1

They work together for 2 hours then the amount of work finished: 2*(1/3 + 1/12) = 5/6
The work remaining for Sam to finish: 1 - 5/6 =1/6
Hours need for Sam to finish: 1/6 : 1/3 = 1/2 hour = 30 mins
_________________

Never forget what you are fighting for...
and when your mind and your body tell you to quit. Your heart will tell you to fight.


Last edited by Kingsman on 21 Jan 2016, 17:56, edited 1 time in total.

Kudos [?]: 13 [0], given: 58

Manager
Manager
User avatar
Joined: 21 Jan 2014
Posts: 102

Kudos [?]: 26 [0], given: 46

GMAT 1: 500 Q32 V28
GPA: 4
Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 21 Jan 2016, 13:59
CounterSniper wrote:
in an hour sam can do 1/3 and for mark it is 1/12
sam's efficiency =100/3=33.33
mark's efficiency = 100/12=8.33
in two hours they completed = 83.32% of the work
work remaining = 16.68 %
time take by sam in minutes = (16.68/33.33)*60 =30.027 = ~30 minutes


I have never used this method but looks very interesting (like a jolly you can use in difficult situations)!!!

Is there a name for it?

I used this method anyway:
Sam can do 1/3 of the job in 1 hour. Mark 1/12 in one hour.
They work together 2 hours so = 1/3*2 + 1/12*2= 5/6. This is the amount of work the have already done.
Now to estimate how many minutes left to Sam, we can simply subtract the rate of Sam to what is done by Sam and Mark, which is = 1/3 - 5/6 = 1/2. So Sam left with 1/2 of hour = 30 mins.

Kudos [?]: 26 [0], given: 46

Director
Director
avatar
P
Joined: 22 May 2016
Posts: 819

Kudos [?]: 266 [0], given: 552

Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 27 Sep 2017, 10:53
Bunuel wrote:
Working at a constant rate, Sam can finish a job in 3 hours. Mark, also working at a constant rate, can finish the same job in 12 hours. If they work together for 2 hours, how many minutes will it take Sam to finish the job, working alone at his constant rate?

A. 5
B. 20
C. 30
D. 60
E. 120

Standard \(rt = W\) works well here

Sam's rate = \(\frac{1}{3}\)

Mark's rate = \(\frac{1}{12}\)

1) Rate at which they work together:

\((\frac{1}{3}\) + \(\frac{1}{12})\) = \(\frac{15}{36}\) = \(\frac{5}{12}\) is combined rate

2) In two hours, they finish how much work? \(W = rt\)

W = \((\frac{5}{12} * 2) = \frac{5}{6}\) of work is finished

3) Time, in minutes, for Sam to finish remaining work alone? (Work/Sam's rate) = Sam's time. Then convert hours to minutes.

\(\frac{1}{6}\) of work remains

\(\frac{\frac{1}{6}}{\frac{1}{3}} =(\frac{1}{6} * 3) =\frac{1}{2}hr\)

\(\frac{1}{2}hr\) = \(30\) minutes*

Answer C

*\(\frac{1}{2}hr\) = 30 minutes is easy. With harder numbers, just multiply any fraction of an hour by 60 to get minutes. Example:

\((\frac{17}{12}hr)\) * (60) = 85 minutes

Kudos [?]: 266 [0], given: 552

Expert Post
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1545

Kudos [?]: 837 [0], given: 5

Re: Working at a constant rate, Sam can finish a job in 3 hours. Mark, als [#permalink]

Show Tags

New post 01 Oct 2017, 12:13
Bunuel wrote:
Working at a constant rate, Sam can finish a job in 3 hours. Mark, also working at a constant rate, can finish the same job in 12 hours. If they work together for 2 hours, how many minutes will it take Sam to finish the job, working alone at his constant rate?

A. 5
B. 20
C. 30
D. 60
E. 120


The rate of Sam is 1/3 and the rate of Mark is 1/12. We can let Sam’s time = 2 + x hours and Mark’s time = 2 hours; thus:

(1/3)(2 + x) + (1/12)(2) = 1

(2 + x)/3 + 1/6 = 1

Multiplying the equation by 6, we have:

4 + 2x + 1 = 6

2x = 1

x = 1/2 hour = 30 minutes

Answer: C
_________________

Jeffery Miller
Head of GMAT Instruction

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

Kudos [?]: 837 [0], given: 5

Re: Working at a constant rate, Sam can finish a job in 3 hours. Mark, als   [#permalink] 01 Oct 2017, 12:13
Display posts from previous: Sort by

Working at a constant rate, Sam can finish a job in 3 hours. Mark, als

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


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®.