It is currently 18 Nov 2017, 03:53

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

Jack and Jill working separately complete a work in 8 days and 12 days

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

Hide Tags

3 KUDOS received
Manager
Manager
avatar
G
Joined: 12 Feb 2017
Posts: 71

Kudos [?]: 21 [3], given: 40

Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 21 Aug 2017, 03:44
3
This post received
KUDOS
8
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

63% (01:32) correct 37% (01:43) wrong based on 145 sessions

HideShow timer Statistics

Jack and Jill working separately complete a work in 8 days and 12 days respectively. If they work on alternate days starting with Jill on the first day, in how many days will the work be completed?

A) 9 1/2 days
B) 9 2/3 days
C) 10 days
D) 10 8/12 days
E) 12 days

kudos if it helps.
[Reveal] Spoiler: OA

Last edited by pushkarajnjadhav on 21 Aug 2017, 05:30, edited 2 times in total.

Kudos [?]: 21 [3], given: 40

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 42249

Kudos [?]: 132554 [0], given: 12326

Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 21 Aug 2017, 03:57
pushkarajnjadhav wrote:
Jack and Jill working separately complete a work in 8 days and 12 days respectively. If they work on alternate days starting with Jill on the first day, in how many days will the work be completed?

A) 9 1/2 days
B) 9 2/3 days
C) 10 days
D) 10 8/12 days
E) 12 days


Renamed the topic. Please check rule 3 here: https://gmatclub.com/forum/rules-for-po ... 33935.html Thank you.
_________________

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 [?]: 132554 [0], given: 12326

Intern
Intern
User avatar
S
Joined: 25 Jul 2011
Posts: 44

Kudos [?]: 5 [0], given: 1058

Location: India
Concentration: Strategy, Operations
GMAT 1: 740 Q49 V41
GPA: 3.5
WE: Engineering (Energy and Utilities)
CAT Tests
Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 21 Aug 2017, 04:02
1
This post was
BOOKMARKED
pushkarajnjadhav wrote:
Jack and Jill working separately complete a work in 8 days and 12 days respectively. If they work on alternate days starting with Jill on the first day, in how many days will the work be completed?

A) 9 1/2 days
B) 9 2/3 days
C) 10 days
D) 10 8/12 days
E) 12 days



Total work done by Jack and Jill in two days =1/12+1/8=5/24
So, 5/24 of total work is done in 2 days so 20/24 of total work will be done in 8 days..
Jill will work on 9th day and further complete...1/12 or we can say 2/24 of total work on 9th day..
So total work done till 9th day will be 20/24+2/24=22/24...remaining work =1-22/24=2/24..
as Jack does 1/8 or 3/24 work in 1 day, remaining 2/24 work will be done by Jack in 2/3 days ...
So total 9 2/3 days..its 600 level
_________________

Please hit kudos button below if you found my post helpful..TIA

Kudos [?]: 5 [0], given: 1058

1 KUDOS received
Intern
Intern
avatar
B
Joined: 08 Jun 2015
Posts: 21

Kudos [?]: 2 [1], given: 36

Location: United States
Concentration: Finance, Economics
WE: Engineering (Other)
Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 21 Aug 2017, 05:26
1
This post received
KUDOS
Jack : Jill
Days: 8 : 12 LCM(8,12) = 24 So let 24 be the total work.
Rate: 3 : 2 24 total work divided by days to finish work gives rate.

Now, In 1 day Jack can finish 3 parts of total work and Jill can finish 2 parts of total work.

So, If Jill starts the work and Jack follows him next day then in 2 days they finish 5 parts of work.

Our total work is 24. So 24/5=4(only proper quotient). Hence in 4X2= 8days they finish 20 parts of work.

Remaining part = 4. Again Jill will start and finish his 2 part in 1 day. So in 9 days 22 parts of work is finished.

Remaining part = 2. Jack's turn who finish 3 parts of work in 1 day. So 2 part is finished in 2/3 day.

Hence Total days required = 8 + 1 + 2/3 = 9 2/3.

Although this solution seems to be lengthy but once understood then it is very easy to use.

Kudos [?]: 2 [1], given: 36

1 KUDOS received
BSchool Forum Moderator
User avatar
D
Joined: 26 Feb 2016
Posts: 1596

Kudos [?]: 669 [1], given: 17

Location: India
Concentration: General Management, Leadership
WE: Sales (Retail)
Premium Member CAT Tests
Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 21 Aug 2017, 08:22
1
This post received
KUDOS
1
This post was
BOOKMARKED
Let the total number of units be 96.

Since Jack completes the work in 8 days, he must be completing 12 units/day
Similarly, since Jill completes the work in 12 days, he must be completing 8 units/day

It has been given that they work alternate days with Jill starting the work on the first day
In a span of 2 days, both Jack and Jill will cover 20 units of the work
So they would have completed 80 units in 8 days and on the 9th day Jill completes 8 units(making total 88 units)

Now, for the remaining 8 units, Jack would have to work \(\frac{2}{3}\) day.

The total time taken to complete the work is \(9\frac{2}{3}\) days(Option B)
_________________

Stay hungry, Stay foolish

2017-2018 MBA Deadlines

Class of 2020: Rotman Thread | Schulich Thread
Class of 2019: Sauder Thread

Kudos [?]: 669 [1], given: 17

Manager
Manager
User avatar
S
Joined: 13 Apr 2013
Posts: 211

Kudos [?]: 109 [0], given: 655

Premium Member
Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 31 Aug 2017, 03:46
pushpitkc wrote:
Let the total number of units be 96.

Since Jack completes the work in 8 days, he must be completing 12 units/day
Similarly, since Jill completes the work in 12 days, he must be completing 8 units/day

It has been given that they work alternate days with Jill starting the work on the first day
In a span of 2 days, both Jack and Jill will cover 20 units of the work
So they would have completed 80 units in 8 days and on the 9th day Jill completes 8 units(making total 88 units)

Now, for the remaining 8 units, Jack would have to work \(\frac{2}{3}\) day.

The total time taken to complete the work is \(9\frac{2}{3}\) days(Option B)


Best and very comprehensive approach.

Thanks...It helps
_________________

"Success is not as glamorous as people tell you. It's a lot of hours spent in the darkness."

Kudos [?]: 109 [0], given: 655

Director
Director
avatar
P
Joined: 14 Nov 2014
Posts: 617

Kudos [?]: 104 [0], given: 46

Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 31 Aug 2017, 07:17
lets take total work = 24 unit (it can be easily divisible by 8 and 12)
jack = 24/8 = 3 unit /day
Jill = 24/12 = 2 unit /day
To complete 24 unit alternate days.
2U,3U,2U,3U,2U,3U,2U,3U,2U =22 unit in 9 days ...

Rest Jack have to finish
He will take 2/3 days
total 9 2/3

Kudos [?]: 104 [0], given: 46

Expert Post
1 KUDOS received
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1684

Kudos [?]: 900 [1], given: 5

Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 02 Sep 2017, 07:21
1
This post received
KUDOS
Expert's post
pushkarajnjadhav wrote:
Jack and Jill working separately complete a work in 8 days and 12 days respectively. If they work on alternate days starting with Jill on the first day, in how many days will the work be completed?

A) 9 1/2 days
B) 9 2/3 days
C) 10 days
D) 10 8/12 days
E) 12 days


Jack’s rate is 1/8 and Jill’s rate is 1/12.

In the first day, Jill completes 1/12 of the job. In the second day, Jack completes 1/8 of the job. Thus, in the first two days, Jill and Jack complete 1/12 + 1/8 = 2/24 + 3/24 = 5/24 of the job. If we multiply the amount of work done in two days by 4, we will have 20/24 of the job completed by Jill and Jack in 8 days. On the ninth day, Jill completes another 1/12, or 2/24, of the job. So, the total amount of work done so far is 22/24 of the job. We need the last 2/24 of the job to be completed, and it will be completed by Jack, whose rate is 1/8. Since (2/24)/(1/8) = 16/24 = 2/3, Jack needs only 2/3 of a day to complete the last 2/24 of the job. Thus, to complete the entire job, they need 9 2/3 days.

Answer: B
_________________

Jeffery Miller
Head of GMAT Instruction

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

Kudos [?]: 900 [1], given: 5

Expert Post
Target Test Prep Representative
User avatar
S
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 1684

Kudos [?]: 900 [0], given: 5

Re: Jack and Jill working separately complete a work in 8 days and 12 days [#permalink]

Show Tags

New post 05 Sep 2017, 17:47
pushkarajnjadhav wrote:
Jack and Jill working separately complete a work in 8 days and 12 days respectively. If they work on alternate days starting with Jill on the first day, in how many days will the work be completed?

A) 9 1/2 days
B) 9 2/3 days
C) 10 days
D) 10 8/12 days
E) 12 days

kudos if it helps.


Jack’s rate is 1/8 and Jill’s rate is 1/12.

In the first day, Jill completes 1/12 of the job. In the second day, Jack completes 1/8 of the job. Thus, in the first two days, Jill and Jack complete 1/12 + 1/8 = 2/24 + 3/24 = 5/24 of the job. If we multiply the amount of work done in two days by 4, we will have 20/24 of the job completed by Jill and Jack in 8 days. On the ninth day, Jill completes another 1/12, or 2/24, of the job. So, the total amount of work done so far is 22/24 of the job. We need the last 2/24 of the job to be completed, and it will be completed by Jack, whose rate is 1/8. Since (2/24)/(1/8) = 16/24 = 2/3, Jack needs only 2/3 of a day to complete the last 2/24 of the job. Thus, to complete the entire job, they need 9 2/3 days.

Answer: B
_________________

Jeffery Miller
Head of GMAT Instruction

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

Kudos [?]: 900 [0], given: 5

Re: Jack and Jill working separately complete a work in 8 days and 12 days   [#permalink] 05 Sep 2017, 17:47
Display posts from previous: Sort by

Jack and Jill working separately complete a work in 8 days and 12 days

  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®.