A type A machine can complete a job in 5 hours and a type B : GMAT Problem Solving (PS)
Check GMAT Club Decision Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 24 Jan 2017, 07:43

# STARTING SOON:

How to Get Off the MBA Waitlist: YouTube Live with Personal MBA Coach  |  Click Here to Join the Session

### 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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# A type A machine can complete a job in 5 hours and a type B

Author Message
TAGS:

### Hide Tags

Current Student
Joined: 29 Jan 2005
Posts: 5238
Followers: 25

Kudos [?]: 378 [0], given: 0

A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 05:40
2
This post was
BOOKMARKED
00:00

Difficulty:

25% (medium)

Question Stats:

72% (01:59) correct 28% (01:21) wrong based on 249 sessions

### HideShow timer Statistics

A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?

A. 1/5
B. 29/35
C. 5/6
D. 35/29
E. 35/12
[Reveal] Spoiler: OA

Last edited by GMATT73 on 01 Dec 2005, 08:09, edited 1 time in total.
Director
Joined: 13 Nov 2003
Posts: 790
Location: BULGARIA
Followers: 1

Kudos [?]: 47 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 07:23
Can you, please elaborate on the meaning of" together and independently"
Thanx
Current Student
Joined: 29 Jan 2005
Posts: 5238
Followers: 25

Kudos [?]: 378 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 07:40
1
This post was
BOOKMARKED
BG wrote:
Can you, please elaborate on the meaning of" together and independently"
Thanx

I was also initially confused by such verbiage. However, this phrasing isn`t just Kaplish, it appears over and over again in various prep materials, so just accept it as "the machines/people/computers etc. work at their full capacity without complementing each other."

Hope that helps.
SVP
Joined: 28 May 2005
Posts: 1723
Location: Dhaka
Followers: 7

Kudos [?]: 327 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:10
Matt I am getting 10/7

A need 5 hours to complete

and B needs 10 hours to compete

so 2A + 3B will complete 2/5 + 3/10 or 7/10 portion of the job in 1 hour

so the whole job will take 10/7 hours....

am I missing something....
_________________

hey ya......

Current Student
Joined: 29 Jan 2005
Posts: 5238
Followers: 25

Kudos [?]: 378 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:12
remgeo wrote:
I am also getting 10/7

2*1/5 + 3*1/10 = 10/7

Even with the edit, you are still missing a step.
SVP
Joined: 24 Sep 2005
Posts: 1890
Followers: 19

Kudos [?]: 293 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:13
hik, it kept me pondering for a while ...wonder what i missed here (without the edition)
Matt, take good rest after such a busy week!!

Last edited by laxieqv on 01 Dec 2005, 08:16, edited 1 time in total.
SVP
Joined: 28 May 2005
Posts: 1723
Location: Dhaka
Followers: 7

Kudos [?]: 327 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:16
now D should be the answer.

A need 5 hours to complete

and B needs 7 hours to compete

so 2A + 3B will complete 2/5 + 3/7 or 29/35 portion of the job in 1 hour

so the whole job will take 35/29 hours....
_________________

hey ya......

Current Student
Joined: 29 Jan 2005
Posts: 5238
Followers: 25

Kudos [?]: 378 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:18
This is from the Kaplan White Course Book. The OE is a page long but makes no logical sense.
Director
Joined: 24 Oct 2005
Posts: 659
Location: London
Followers: 1

Kudos [?]: 15 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:21
GMATT73 wrote:
remgeo wrote:
I am also getting 10/7

2*1/5 + 3*1/10 = 10/7

Even with the edit, you are still missing a step.

2*1/5 + 3*1/7 = 29/35

Ans = 35/29

I still cant see what step I missed
Current Student
Joined: 29 Jan 2005
Posts: 5238
Followers: 25

Kudos [?]: 378 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:33
remgeo wrote:
GMATT73 wrote:
remgeo wrote:
I am also getting 10/7

2*1/5 + 3*1/10 = 10/7

Even with the edit, you are still missing a step.

2*1/5 + 3*1/7 = 29/35

Ans = 35/29

I still cant see what step I missed

The step highlighted in red. When did you decide to include it?
Director
Joined: 24 Oct 2005
Posts: 659
Location: London
Followers: 1

Kudos [?]: 15 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 08:41
GMATT73 wrote:
remgeo wrote:
GMATT73 wrote:
remgeo wrote:
I am also getting 10/7

2*1/5 + 3*1/10 = 10/7

Even with the edit, you are still missing a step.

2*1/5 + 3*1/7 = 29/35

Ans = 35/29

I still cant see what step I missed

The step highlighted in red. When did you decide to include it?

Well, I had included that earlier as well.
10/7 was my conclusion
2/5 + 3/10 was the evidence
The assumption which is hidden was that I had taken the reverse of 7/10 to get the answer

Dont you think I need some rest !!
Senior Manager
Joined: 11 Nov 2005
Posts: 328
Location: London
Followers: 1

Kudos [?]: 11 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

01 Dec 2005, 09:22
Ans. D

My expl. A needs 5 hours to complete the job
2A need 5/2 hours to complete the job,

similarly 3B need 7/3 hours to complete the job

Lets consider 2A and 3B as single entity (X, Y)

so

1/X + 1/Y = 1/Z Z is the time to complete the job if working together.

1/(2/5) + 1/(7/3) =1/Z
2/5 + 3/7 =1/Z
29/35 = 1/Z

Z = 35/29

so if 2A and 3 B working together, they would need 35/29 hours to complete the job.

WORKING TOHETHER and INDEPENDENTLY means they work together without interfering each other hence they use their full potential to complete the job!

Does this sound sensible????

or simply.

1/5+1/5+1/7+1/7+1/7 =1/Z ( Z: time to work together)

Z = 35/29
Senior Manager
Joined: 11 May 2004
Posts: 458
Location: New York
Followers: 1

Kudos [?]: 47 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

02 Dec 2005, 13:01
Machine A's rate =1/5
Machine B's rate = 1/7

We have 2 A machines and 3 B machines = 1/5+1/5+1/7+1/7+1/7
Find the common denominator ie 35 and solve

You will get 29/35. This means that the machines can do 29/35 of the work in 1 hour. The question is asking how many hours does it take?

So, you take the inverse and you get 35/29.
Senior Manager
Joined: 03 Nov 2005
Posts: 396
Location: Chicago, IL
Followers: 3

Kudos [?]: 50 [0], given: 17

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

02 Dec 2005, 15:48
Basic formula for the rate 1/a+1/b+1/c.....=1/Z time=Z

Rate for is A 1/5 and B works at the rate 1/7; 2A=2/5 and 3B=3/7

2/5+3/7=29/35 Flip it. 35/29. That Kaplish stuff can only appear at the beginning of Math section. Actual test questions appear to be much harder than that.
_________________

Hard work is the main determinant of success

Intern
Joined: 16 Sep 2013
Posts: 2
Location: United States
GPA: 3.75
WE: Information Technology (Consulting)
Followers: 0

Kudos [?]: 5 [0], given: 1

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

26 Sep 2014, 11:50
A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?

--just remember rate*time=job
Lets consider they both need to type for t hours to get the job done..

So, rate*time=job (Here job is 1 as it needs to be completed)
rate for type A machine =1/5 -- effective rate for 2 machines =2/5
similarly for type B machine effective rate for 2 machines =3/7

Finally we have,
(2/5)*t + (3/7)*t=1
t(29/35)=1
t=35/29

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 13542
Followers: 578

Kudos [?]: 163 [0], given: 0

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

10 Oct 2016, 05:54
Hello from the GMAT Club BumpBot!

Thanks to another GMAT Club member, I have just discovered this valuable topic, yet it had no discussion for over a year. I am now bumping it up - doing my job. I think you may find it valuable (esp those replies with Kudos).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email.
_________________
Math Forum Moderator
Status: QA & VA Forum Moderator
Joined: 11 Jun 2011
Posts: 2306
Location: India
GPA: 3.5
Followers: 94

Kudos [?]: 639 [0], given: 317

Re: A type A machine can complete a job in 5 hours and a type B [#permalink]

### Show Tags

10 Oct 2016, 06:00
GMATT73 wrote:
A type A machine can complete a job in 5 hours and a type B machine can complete the job in 7 hours. How many hours will it take 2 type A machines and 3 type B machines working together and independently to complete the job?

A. 1/5
B. 29/35
C. 5/6
D. 35/29
E. 35/12

Let the total work be 35 ( LCM of 5 & 7 )

So, Efficiency of type A machines = 35/5 => 7
Efficiency of type A machines = 35/7 => 5

Quote:
How many hours will it take 2 type A machines and 3 type B machines working together

Combined efficiency will be -

Type A = 2*7 => 14
Type B = 3*5 => 15

Total efficiency is 14 + 15 = 29

So, Time taken will be 35/29

Hence correct answer will be (D) 35/29

_________________

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 )

Re: A type A machine can complete a job in 5 hours and a type B   [#permalink] 10 Oct 2016, 06:00
Similar topics Replies Last post
Similar
Topics:
14 Together, 15 type A machines and 7 type B machines can compl 4 06 Mar 2014, 20:44
113 Machine A can complete a certain job in x hours. Machine B 29 05 Nov 2011, 12:23
39 Two consultants can type up a report in 12.5 hours and edit 12 16 Jan 2012, 09:01
8 A can complete the job in 2 hours and B can complete the sam 6 17 Mar 2011, 04:21
8 Machine A working alone can complete a job in 3 1/2 hours 7 08 Mar 2011, 01:23
Display posts from previous: Sort by