Last visit was: 13 Dec 2024, 10:40 It is currently 13 Dec 2024, 10:40
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
User avatar
Bunuel
User avatar
Math Expert
Joined: 02 Sep 2009
Last visit: 13 Dec 2024
Posts: 97,873
Own Kudos:
685,588
 []
Given Kudos: 88,268
Products:
Expert reply
Active GMAT Club Expert! Tag them with @ followed by their username for a faster response.
Posts: 97,873
Kudos: 685,588
 []
Kudos
Add Kudos
3
Bookmarks
Bookmark this Post
User avatar
GMATBusters
User avatar
GMAT Tutor
Joined: 27 Oct 2017
Last visit: 10 Dec 2024
Posts: 1,930
Own Kudos:
6,044
 []
Given Kudos: 240
WE:General Management (Education)
Expert reply
Posts: 1,930
Kudos: 6,044
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
eakabuah
User avatar
Retired Moderator
Joined: 18 May 2019
Last visit: 15 Jun 2022
Posts: 782
Own Kudos:
1,078
 []
Given Kudos: 101
Posts: 782
Kudos: 1,078
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
User avatar
CareerGeek
Joined: 20 Jul 2017
Last visit: 12 Dec 2024
Posts: 1,297
Own Kudos:
3,784
 []
Given Kudos: 162
Location: India
Concentration: Entrepreneurship, Marketing
GMAT 1: 690 Q51 V30
WE:Education (Education)
GMAT 1: 690 Q51 V30
Posts: 1,297
Kudos: 3,784
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Formula: Work = Rate*time

Let the total work = LCM (5, 7) = 35 units

Rate of A, \(R_A = \frac{35}{5} = 7 u\)nits/hr &
Rate of B, \(R_B = \frac{35}{7} = 5\) units/hr

Rate of 2 type A & 3 type B = \(2*R_A + 3*R_B\) \(= 2*7 + 3*5 = 29\)

--> Time taken = Work/Rate = \(\frac{35}{29}\)

IMO Option D
User avatar
Mohammadmo
Joined: 29 Jun 2019
Last visit: 03 Nov 2022
Posts: 352
Own Kudos:
229
 []
Given Kudos: 16
Posts: 352
Kudos: 229
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
2A machines can do 2/5 of a job in one hour.
3B machines can do 3/7 of a job in one hour.
So, (2/5 + 3/7)X=1
X=35/29
Option D

Posted from my mobile device
User avatar
madgmat2019
Joined: 01 Mar 2019
Last visit: 17 Sep 2021
Posts: 588
Own Kudos:
557
 []
Given Kudos: 207
Location: India
Concentration: Strategy, Social Entrepreneurship
GMAT 1: 580 Q48 V21
GPA: 4
Products:
GMAT 1: 580 Q48 V21
Posts: 588
Kudos: 557
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Together time = x
2/A + 3/B = 1/x
2/5 + 3/7 = 1/x
29/35 =1/x
x = 35/29

OA:D

Posted from my mobile device
User avatar
nick1816
User avatar
Retired Moderator
Joined: 19 Oct 2018
Last visit: 12 Dec 2024
Posts: 1,859
Own Kudos:
7,094
 []
Given Kudos: 707
Location: India
Posts: 1,859
Kudos: 7,094
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Assume total work= LCM(5,7)=35 units

Type A machine can do 7 units/hour
Type B machine can do 5 units/hour

Total time taken by 2 type A machines and 3 type B machines working together= \(\frac{35}{(2*7+3*5)}\)= \(\frac{35}{29}\) hours

D
User avatar
Kinshook
User avatar
GMAT Club Legend
Joined: 03 Jun 2019
Last visit: 13 Dec 2024
Posts: 5,423
Own Kudos:
4,599
 []
Given Kudos: 161
Location: India
GMAT 1: 690 Q50 V34
WE:Engineering (Transportation)
Products:
GMAT 1: 690 Q50 V34
Posts: 5,423
Kudos: 4,599
 []
1
Kudos
Add Kudos
1
Bookmarks
Bookmark this Post
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

Work done by type A machine in 1 hour = 1/5
Work done by type B machine in 1 hour = 1/7

Work done by 2 type A machines and 3 type B machines in 1 hour = 2/5 + 3/7 = (14+15)/35 = 29/35

Hours taken by 2 type A machines and 3 type B machines to complete the job = 35/29 hours

IMO D
User avatar
unraveled
Joined: 07 Mar 2019
Last visit: 12 Dec 2024
Posts: 2,741
Own Kudos:
2,010
 []
Given Kudos: 764
Location: India
WE:Sales (Energy)
Posts: 2,741
Kudos: 2,010
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
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

Work done in 1 hour by a Type A machines = \(\frac{1}{5}\) units
Work done in 1 hour by 2 Type A machines = \(\frac{2}{5}\) units

Work done in 1 hour by a Type B machines = \(\frac{1}{7}\) units
Work done in 1 hour by 3 Type B machines = \(\frac{3}{7}\) units

Work done in 1 hour by 2 Type A and 3 Type B machines = \(\frac{2}{5} + \frac{3}{7}\) = \(\frac{29}{35}\) units
Thus time taken to complete the job by the five machines = \(\frac{1}{29/35}\) = \(\frac{35}{29}\) hours

IMO Answer D.
avatar
LalitaSiri
Joined: 05 Aug 2018
Last visit: 06 Mar 2020
Posts: 71
Own Kudos:
72
 []
Given Kudos: 7
Location: Thailand
Concentration: Finance, Entrepreneurship
GPA: 3.68
WE:Business Development (Energy)
Posts: 71
Kudos: 72
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
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

A machine complete a job in 5 hours, so in 1 hour A machine can complete 1/5 of jobs.
B machine complete a job in 7 hours, so in 1 hour B machine can complete 1/7 of jobs.

2 A machines, can complete 2/5 jobs per hour
and 3 B machines, can complete 3/7 jobs per hour

working together, they can complete 2/5 + 3/7 = 29/35

Thus, it requires 1/ (29/35) = 35/29 hours to complete the job.

Therefore D is the correct answer
User avatar
Archit3110
User avatar
GMAT Club Legend
Joined: 18 Aug 2017
Last visit: 13 Dec 2024
Posts: 8,118
Own Kudos:
4,498
 []
Given Kudos: 243
Status:You learn more from failure than from success.
Location: India
Concentration: Sustainability, Marketing
GMAT Focus 1: 545 Q79 V79 DI73
GPA: 4
WE:Marketing (Energy)
Products:
GMAT Focus 1: 545 Q79 V79 DI73
Posts: 8,118
Kudos: 4,498
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
rate of A; 1/5 and rate of B ; 1/7
rate of 2 A and 3 B ; 2/5 and 3/7
together rate ; 2/5+3/7 =29/35 ; time ; 35/29
IMO D


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
User avatar
siddharthkapoor
User avatar
GMAT Club Reviews PM Intern
Joined: 10 Apr 2018
Last visit: 04 Jul 2024
Posts: 531
Own Kudos:
784
 []
Given Kudos: 522
Location: India
Schools: ISB'22 (D)
GMAT 1: 680 Q48 V34
GPA: 3.3
Products:
Schools: ISB'22 (D)
GMAT 1: 680 Q48 V34
Posts: 531
Kudos: 784
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Quote:
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

Rate=\(\frac{Work}{Time taken}\)

Let the required work to do be 1 unit.

So, rate of doing work of machine A=\(\frac{1}{5}\)
Thus, rate of doing work of 2 machine A=\(\frac{2}{5}\)
Similarly, rate of doing work of machine B=\(\frac{1}{7}\)
Thus, rate of doing work of 3 machine B=\(\frac{3}{7}\)

Total rate= \(\frac{2}{5}+\frac{3}{7}\)=\(\frac{29}{35}\)
So, Total time=1/29/35=\(\frac{35}{29}\)

Thus, the correct answer is option D.
User avatar
exc4libur
Joined: 24 Nov 2016
Last visit: 22 Mar 2022
Posts: 1,710
Own Kudos:
1,394
 []
Given Kudos: 607
Location: United States
Posts: 1,710
Kudos: 1,394
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
Quote:
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

rate=job*time, rA=1/5, rB=1/7

job/rate=time, 1/(2a+3b)=t, 1/(2/5+3/7)=t, t=35/29

Answer (D)
User avatar
lacktutor
Joined: 25 Jul 2018
Last visit: 23 Oct 2023
Posts: 663
Own Kudos:
1,221
 []
Given Kudos: 69
Posts: 663
Kudos: 1,221
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
a type A machine —\(\frac{1}{5}\)
a type B machine—\(\frac{1}{7}\)
———————
\(2( \frac{1}{5})+ 3( \frac{1}{7})\)= \(\frac{1}{x}\) ???

—> \(\frac{2}{5}+ \frac{3}{7}\)= \(\frac{(14+ 15)}{35}\)=\(\frac{1}{x}\)
—> x = \(\frac{35}{29}\)

The answer is D.

Posted from my mobile device
User avatar
joohwangie
Joined: 17 Jan 2019
Last visit: 13 Dec 2024
Posts: 256
Own Kudos:
217
 []
Given Kudos: 54
Concentration: Leadership, Sustainability
Schools: Stanford
Products:
Schools: Stanford
Posts: 256
Kudos: 217
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
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?

(1/5)+(1/7)=12/35--rate
time is reciprocal of rate, therefore, 35/12 hours for 1A and 1B

2A and 3B
2/5+3/7=14/35+15/35=29/35
reciprocal = 35/29
Therefore, D
avatar
sheikhtraders
Joined: 05 Oct 2019
Last visit: 18 Dec 2019
Posts: 3
Own Kudos:
1
 []
Posts: 3
Kudos: 1
 []
1
Kudos
Add Kudos
Bookmarks
Bookmark this Post
A complete the 1/5 of work in one hour and B 1/7 in one hour.

so 2A+ 3B in one hour is (2/5+3/7) of work
==> 29/35 work in one hour
==> total work in 1/(29/35) = 35/29

Ans:: D

Posted from my mobile device
Moderator:
Math Expert
97873 posts