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

It is currently 19 Jul 2019, 13:53

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

Sam can repair a machine in 15 days and Ross can repair in 25 days

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

Hide Tags

Find Similar Topics 
Manager
Manager
avatar
B
Joined: 03 Feb 2017
Posts: 74
Location: Australia
GMAT 1: 720 Q48 V40
Sam can repair a machine in 15 days and Ross can repair in 25 days  [#permalink]

Show Tags

New post 24 Jun 2017, 03:02
1
9
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

66% (02:08) correct 34% (02:33) wrong based on 156 sessions

HideShow timer Statistics


Sam can repair a machine in 15 days and Ross can repair the same machine in 25 days. If they decide to repair the machine on alternate days, with Ross on the first day, followed by Sam on the second day and so on till the repair is completed, how many days do they take to complete the repair work.

A) 17
B) 18
C) 19
D) 20
E) 21
Most Helpful Community Reply
Senior Manager
Senior Manager
User avatar
B
Joined: 28 Jun 2015
Posts: 286
Concentration: Finance
GPA: 3.5
Re: Sam can repair a machine in 15 days and Ross can repair in 25 days  [#permalink]

Show Tags

New post 24 Jun 2017, 04:08
5
1
1
Work done by Sam in one day = 1/15, in Ross = 1/25.
Total work done by Sam in the first day and Ross in the second day = 1/15 + 1/25 = 8/75.

No. of days to complete the work: n(8/75) = 1
n = 75/8 = 9.375.

So, it will take 9.375 two day's work, hence 9.375 * 2 = ~19 days.
_________________
I used to think the brain was the most important organ. Then I thought, look what’s telling me that.
General Discussion
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 56300
Re: Sam can repair a machine in 15 days and Ross can repair in 25 days  [#permalink]

Show Tags

New post 24 Jun 2017, 06:49
1
danlew wrote:
Sam can repair a machine in 15 days and Ross can repair the same machine in 25 days. If they decide to repair the machine on alternate days, with Ross on the first day, followed by Sam on the second day and so on till the repair is completed, how many days do they take to complete the repair work.

A) 17
B) 18
C) 19
D) 20
E) 21


Use LCM:
Portion of the work done by Sam is 1/15 = 5/75;
Portion of the work done by Ross is 1/25 = 3/75.

Together in 2*9 = 18 days they'll do (5 + 3)*9 = 72 parts out of 75. On the 19th day Sam will do the remaining job. So, the answer is 19.

Answer: C.
_________________
Intern
Intern
avatar
B
Joined: 23 May 2017
Posts: 6
Re: Sam can repair a machine in 15 days and Ross can repair in 25 days  [#permalink]

Show Tags

New post 26 Oct 2018, 03:27
Together in 2*9 = 18 days they'll do (5 + 3)*9 = 72 parts out of 75. On the 19th day Sam will do the remaining job. So, the answer is 19.

Can someone explain this part?
Board of Directors
User avatar
P
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 4512
Location: India
GPA: 3.5
WE: Business Development (Commercial Banking)
GMAT ToolKit User
Re: Sam can repair a machine in 15 days and Ross can repair in 25 days  [#permalink]

Show Tags

New post 26 Oct 2018, 07:59
1
danlew wrote:
Sam can repair a machine in 15 days and Ross can repair the same machine in 25 days. If they decide to repair the machine on alternate days, with Ross on the first day, followed by Sam on the second day and so on till the repair is completed, how many days do they take to complete the repair work.

A) 17
B) 18
C) 19
D) 20
E) 21

Let the total work be 75 units.

Efficiency of Sam = 5 units/day
Efficiency of Ross = 3 units/day

Since they work alone on alternate days then they complete 8 units of work in 2 days..

That is they complete 72 units of work in 18 days (Simply multiply by 9)

After that 3 units of work is left which Ross completes in 1 days...

So, the work will be completed in 19 days, Answer must be (C) 19 days
_________________
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
Manager
avatar
G
Joined: 14 Jun 2018
Posts: 222
Re: Sam can repair a machine in 15 days and Ross can repair in 25 days  [#permalink]

Show Tags

New post 26 Oct 2018, 12:52
Sam does 100/15% or 6.67% work in 1 day
Ross does 100/25 or 4% work in 1 day
Total work done in 2 days = 6.67+4 = 10.67% work
10.67 * 9 = 96% work in 18 days
remaining 4% done in the 19th day
GMAT Club Bot
Re: Sam can repair a machine in 15 days and Ross can repair in 25 days   [#permalink] 26 Oct 2018, 12:52
Display posts from previous: Sort by

Sam can repair a machine in 15 days and Ross can repair in 25 days

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





Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne