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

It is currently 22 Sep 2018, 15:50

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

If it takes Jacob x hours to complete a project and it takes Mike y

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 49303
If it takes Jacob x hours to complete a project and it takes Mike y  [#permalink]

Show Tags

New post 17 Apr 2018, 05:14
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

79% (00:27) correct 21% (00:30) wrong based on 82 sessions

HideShow timer Statistics

If it takes Jacob x hours to complete a project and it takes Mike y hours to complete the same project, how many hours will it take them to complete the project if they are working together?

A. xy/(x+y)

B. (x+y)/(xy)

C. x+y

D. xy

E. x–y

_________________

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

Manager
Manager
User avatar
S
Joined: 28 Nov 2017
Posts: 145
Location: Uzbekistan
Premium Member
Re: If it takes Jacob x hours to complete a project and it takes Mike y  [#permalink]

Show Tags

New post 17 Apr 2018, 06:02
Bunuel wrote:
If it takes Jacob x hours to complete a project and it takes Mike y hours to complete the same project, how many hours will it take them to complete the project if they are working together?

A. xy/(x+y)

B. (x+y)/(xy)

C. x+y

D. xy

E. x–y


\(\frac{1}{x} + \frac{1}{y} = \frac{1}{z}\)

\(z = \frac{xy}{(x+y)}\)

Answer: A
_________________

Kindest Regards!
Tulkin.

Director
Director
User avatar
G
Joined: 31 Oct 2013
Posts: 577
Concentration: Accounting, Finance
GPA: 3.68
WE: Analyst (Accounting)
If it takes Jacob x hours to complete a project and it takes Mike y  [#permalink]

Show Tags

New post 18 Apr 2018, 17:45
Bunuel wrote:
If it takes Jacob x hours to complete a project and it takes Mike y hours to complete the same project, how many hours will it take them to complete the project if they are working together?

A. xy/(x+y)

B. (x+y)/(xy)

C. x+y

D. xy

E. x–y


Jacob's 1 hour's work = 1/x
Mike's 1 hour's work=1/y

Jacob and Mike's 1 hour's work=1/x + 1/y
= (x+y)/xy

Now (x+y)/xy is done in 1 hour
So, the entire work will be done by = xy/(x+y), which is option A.
Target Test Prep Representative
User avatar
G
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2835
Re: If it takes Jacob x hours to complete a project and it takes Mike y  [#permalink]

Show Tags

New post 19 Apr 2018, 16:50
Bunuel wrote:
If it takes Jacob x hours to complete a project and it takes Mike y hours to complete the same project, how many hours will it take them to complete the project if they are working together?

A. xy/(x+y)

B. (x+y)/(xy)

C. x+y

D. xy

E. x–y


Jacob’s rate is 1/x, and Mike’s rate is 1/y. We can create the following combined rate expression:

1/x + 1/y = y/xy + x/xy = (x + y)/xy

Since time is inverse of rate, it will take them xy/(x+y) hours to complete the project.

Answer: A
_________________

Jeffery Miller
Head of GMAT Instruction

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

CEO
CEO
User avatar
D
Joined: 12 Sep 2015
Posts: 2878
Location: Canada
Re: If it takes Jacob x hours to complete a project and it takes Mike y  [#permalink]

Show Tags

New post 25 Aug 2018, 07:02
Top Contributor
Bunuel wrote:
If it takes Jacob x hours to complete a project and it takes Mike y hours to complete the same project, how many hours will it take them to complete the project if they are working together?

A. xy/(x+y)

B. (x+y)/(xy)

C. x+y

D. xy

E. x–y


For work questions, there are two useful rules:

Rule #1: If a person can complete an entire job in k hours, then in one hour, the person can complete 1/k of the job
Example: If it takes Sue 5 hours to complete a job, then in one hour, she can complete 1/5 of the job. In other words, her work rate is 1/5 of the job per hour

Rule #2: If a person completes a/b of the job in one hour, then it will take b/a hours to complete the entire job
Example: If Sam can complete 1/8 of the job in one hour, then it will take him 8/1 hours to complete the job.
Likewise, if Joe can complete 2/3 of the job in one hour, then it will take him 3/2 hours to complete the job.

Let’s use these rules to solve the question. . . .

It takes Jacob x hours to complete a project and it takes Mike y hours to complete the same project
So, applying Rule #1....
Jacob completes 1/x of the job in ONE HOUR
Mike completes 1/y of the job in ONE HOUR
So, in ONE HOUR, the two workers complete 1/x + 1/y of the job

1/x + 1/y = y/xy + x/xy
= (x + y)/xy

In other words, in ONE HOUR, the two workers complete (x + y)/xy of the job
Applying Rule #2, the total time to COMPLETE the job = xy/(x + y)

Answer: A

Cheers,
Brent
_________________

Brent Hanneson – GMATPrepNow.com
Image
Sign up for our free Question of the Day emails

GMAT Club Bot
Re: If it takes Jacob x hours to complete a project and it takes Mike y &nbs [#permalink] 25 Aug 2018, 07:02
Display posts from previous: Sort by

If it takes Jacob x hours to complete a project and it takes Mike y

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

Events & Promotions

PREV
NEXT


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®.