Last visit was: 12 Nov 2024, 22:56 It is currently 12 Nov 2024, 22:56

Close

GRE Prep 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 GRE 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
Verbal Expert
Joined: 18 Apr 2015
Posts: 29944
Own Kudos [?]: 36207 [2]
Given Kudos: 25902
Send PM
Verbal Expert
Joined: 18 Apr 2015
Posts: 29944
Own Kudos [?]: 36207 [0]
Given Kudos: 25902
Send PM
avatar
Manager
Manager
Joined: 17 Feb 2020
Posts: 64
Own Kudos [?]: 69 [0]
Given Kudos: 0
Send PM
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12188 [0]
Given Kudos: 136
Send PM
Re: Working alone, Printers X, Y, and Z can do a certain printin [#permalink]
2
Carcass wrote:
Working alone, Printers X, Y, and Z can do a certain printing job, consisting of a large number of pages, in 12, 15, and 18 hours, respectively. What is the ratio of the time it takes Printer X to do the job, working alone at its rate, to the time it takes Printers Y and Z to do the job, working together at their individual rates?

(A) 4/11
(B) 1/2
(C) 15/22
(D) 22/15
(E) 11/4


----ASIDE-----------------------------------
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. . . .

Printer Y takes 15 hours to complete a job. So, by rule #1, printer Y’s rate is 1/15 of the job per hour
Printer Z takes 18 hours to complete a job. So, by rule #1, printer Z’s rate is 1/18 of the job per hour
So, their combined rate per hour = 1/15 + 1/18
= 6/90 + 5/90
= 11/90
So, working together, printers Y and Z can complete the 11/90 of the job in one hour.
When we apply rule #2, we can conclude that, working together, printers Y and Z will complete the entire job in 90/11 hours.


What is the ratio of the time it takes printer X to do the job, working at its rate, to time it takes printers y and z to do the job?
So, (time for X to complete)/ (time for Y & Z to complete) = 12/(90/11)
= (12)(11/90)
= 22/15

Answer: D
Retired Moderator
Joined: 10 Apr 2015
Posts: 6218
Own Kudos [?]: 12188 [0]
Given Kudos: 136
Send PM
Re: Working alone, Printers X, Y, and Z can do a certain printin [#permalink]
esaktasynov wrote:
Isn't the answer should be C?


The answer is D.
See my post above.

Cheers,
Brent
avatar
Manager
Manager
Joined: 17 Feb 2020
Posts: 64
Own Kudos [?]: 69 [0]
Given Kudos: 0
Send PM
Re: Working alone, Printers X, Y, and Z can do a certain printin [#permalink]
Yeah, you're right, my mistake
Retired Moderator
Joined: 13 Jun 2022
Posts: 105
Own Kudos [?]: 106 [0]
Given Kudos: 29
Send PM
Re: Working alone, Printers X, Y, and Z can do a certain printin [#permalink]
Solution -

Work Formula = (A*B)/(A+B)

X = 12 hours to do a job
Y = 15 hours to do a job
Z = 18 hours to do a job


Together, Y and Z take => (15*18)/(15+18) hours to do the job.


=> 270/33 = 90/11 hours

The ratio of X to (Y and Z) = 12/(90/11) = 12(11)/90 = 132/90 = 22/15

Answer (D)
Prep Club for GRE Bot
Re: Working alone, Printers X, Y, and Z can do a certain printin [#permalink]
Moderators:
GRE Instructor
78 posts
GRE Forum Moderator
37 posts
Moderator
1111 posts
GRE Instructor
234 posts

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