Summer is Coming! Join the Game of Timers Competition to Win Epic Prizes. Registration is Open. Game starts Mon July 1st.

 It is currently 18 Jul 2019, 07:06

### 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

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

# Lois can complete a certain job in x hours and Parnel can complete the

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 56251
Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

04 Apr 2017, 05:28
00:00

Difficulty:

5% (low)

Question Stats:

96% (00:43) correct 4% (02:25) wrong based on 66 sessions

### HideShow timer Statistics

Lois can complete a certain job in x hours and Parnel can complete the same job in y hours. Which of the following expresses, in terms of x and y, the time it would take them to complete the job if they worked together?

A. (x + y)/y
B. xy/y
C. xy/x
D. 2/(xy)
E. xy/(x + y)

_________________
Manager
Status: active
Joined: 25 Jan 2016
Posts: 130
Location: India
Concentration: Finance, Entrepreneurship
GPA: 4
WE: Web Development (Computer Software)
Re: Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

04 Apr 2017, 05:47

1/x + 1/y=Combined rate
time taken would be xy/(x+y)
Manager
Joined: 14 Sep 2016
Posts: 59
Concentration: Finance, Economics
Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

04 Apr 2017, 06:42
Bunuel wrote:
Lois can complete a certain job in x hours and Parnel can complete the same job in y hours. Which of the following expresses, in terms of x and y, the time it would take them to complete the job if they worked together?

A. (x + y)/y
B. xy/y
C. xy/x
D. 2/(xy)
E. xy/(x + y)

E.
Pick numbers

Lois
Job in 10 hours
X=10
$$\frac{1}{10}$$ job an hour

Parnel
Job in 5 hours
Y =5
$$\frac{1}{5}$$ job an hour

Together
x + y = $$\frac{3}{10}$$ job an hour
or 3.33 hours to do the job together.

Plug in x=10 and y=5 into the answer choices until you find 3.33 which is E.
Current Student
Joined: 09 Oct 2016
Posts: 89
Location: United States
GMAT 1: 740 Q49 V42
GPA: 3.49
Re: Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

04 Apr 2017, 07:02
1/x + 1/y (t) = 1

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

t = xy/(x+y)

E

Sent from my iPhone using GMAT Club Forum
Manager
Joined: 06 Dec 2016
Posts: 243
Re: Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

04 Apr 2017, 12:55
1/x + 1/y
y +x/xy
Flip over the fraction

xy/y + x

Intern
Joined: 29 Oct 2017
Posts: 5
Location: Russian Federation
GPA: 3.43
WE: Supply Chain Management (Manufacturing)
Re: Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

18 Aug 2018, 06:36
WORK = TIME x RATE
WORK = 1
T(L)=X, R(L)=1/X
T(P)=Y, R(P)=1/Y

Rate Together= 1/x+1/y= (y+x)/xy
Time together= Work/Rate=1/((y+x)/xy)= xy/(y+x)
Board of Directors
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4512
Location: India
GPA: 3.5
Re: Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

18 Aug 2018, 07:29
Bunuel wrote:
Lois can complete a certain job in x hours and Parnel can complete the same job in y hours. Which of the following expresses, in terms of x and y, the time it would take them to complete the job if they worked together?

A. (x + y)/y
B. xy/y
C. xy/x
D. 2/(xy)
E. xy/(x + y)

Let th total work be xy units

The efficiency of Lois is $$y$$ units/hr
The efficiency of Parnel is $$x$$ units/hr

Combined efficiency of Lois & Parnel is $$(x + y)$$ units/hr

So, the time required by Lois & Parnel is $$\frac{xy}{(x + y)}$$

PS : THIS IS BASICALLY A FORMULA, KNOWING THIS FORMULA CAN HELP DURING THE EXAM
_________________
Thanks and Regards

Abhishek....

PLEASE FOLLOW THE RULES FOR POSTING IN QA AND VA FORUM AND USE SEARCH FUNCTION BEFORE POSTING NEW QUESTIONS

How to use Search Function in GMAT Club | Rules for Posting in QA forum | Writing Mathematical Formulas |Rules for Posting in VA forum | Request Expert's Reply ( VA Forum Only )
Manager
Joined: 20 Jul 2018
Posts: 87
GPA: 2.87
Re: Lois can complete a certain job in x hours and Parnel can complete the  [#permalink]

### Show Tags

18 Aug 2018, 09:08
rate of Lois = 1/x
rate of Parnel = 1/y
combined rate = 1/x + 1/y = x+y/xy

so time = 1/rate = xy/x+y

_________________
Hasnain Afzal

"When you wanna succeed as bad as you wanna breathe, then you will be successful." -Eric Thomas
Re: Lois can complete a certain job in x hours and Parnel can complete the   [#permalink] 18 Aug 2018, 09:08
Display posts from previous: Sort by