GMAT Question of the Day - Daily to your Mailbox; hard ones only

 It is currently 22 Oct 2019, 17:00

### 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

# Three machines are operating simultaneously and independently at diffe

Author Message
TAGS:

### Hide Tags

Math Expert
Joined: 02 Sep 2009
Posts: 58427
Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

17 Apr 2017, 01:09
1
2
00:00

Difficulty:

65% (hard)

Question Stats:

60% (02:03) correct 40% (02:15) wrong based on 129 sessions

### HideShow timer Statistics

Three machines are operating simultaneously and independently at different rates. Machine A produces 1 widget in 4 minutes, Machine B produces 1 widget in 3 minutes, and Machine C produces 1 widget in 5 minutes. If two machines are to be chosen to make 20 widgets in the shortest possible time, approximately how many minutes will it take to produce 20 widgets?

A. 30
B. 34
C. 36
D. 44
E. 70

_________________
Marshall & McDonough Moderator
Joined: 13 Apr 2015
Posts: 1683
Location: India
Re: Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

17 Apr 2017, 02:38
Fastest machines are A and B.

x(1/4 + 1/3) = 20

x = (20 * 12)/7 = 34 mins approx.

Intern
Joined: 12 Feb 2017
Posts: 15
GMAT 1: 740 Q50 V40
Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

17 Apr 2017, 05:32
We will choose machine A and B as these two take least time in producing widgets

For producing 10 widgets B will take 30 mins
In those 30 mins we A will produc 30/4= 7.5 widgets

Still need more 2.5 widgets

Lets take take 34 mins now

Machine A will make 34/4 = 8.5 widgets
Machine B will make 34/3 = 11.33 widgets

8.5 + 11.33 = 19.83

Still not 20

So it should be 36 mins

Where both machines together wil make 21 widgets

Ans C

Sent from my iPhone using GMAT Club Forum
Current Student
Joined: 15 Sep 2013
Posts: 4
Location: United Arab Emirates
GMAT 1: 630 Q38 V39
GPA: 4
Re: Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

17 Apr 2017, 05:38
1
Bunuel wrote:
Three machines are operating simultaneously and independently at different rates. Machine A produces 1 widget in 4 minutes, Machine B produces 1 widget in 3 minutes, and Machine C produces 1 widget in 5 minutes. If two machines are to be chosen to make 20 widgets in the shortest possible time, approximately how many minutes will it take to produce 20 widgets?

A. 30
B. 34
C. 36
D. 44
E. 70

..........R.......T......W
A.......1/4.....
B.......1/3
C.......1/5
A+B...7/12...x.....20

T= W/R
T=20/(7/12)
(20*12)/7 = 34.2

Manager
Joined: 06 Dec 2016
Posts: 231
Re: Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

17 Apr 2017, 12:43
My approach

1/4 + 1/3 = 7/12

7/12 x = 20
x = 34

Senior Manager
Joined: 02 Apr 2014
Posts: 468
Location: India
Schools: XLRI"20
GMAT 1: 700 Q50 V34
GPA: 3.5
Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

25 Feb 2018, 04:41
Hi Bunuel,

I have one question, It is given in the question that, Machines work simultaneouly but independently.
So can machines share work to produce single widget?

Option B - 34 mins, by 33 mins, Machine A would have produced 8 widgets, Machine B would have produced 11 widgets, now the machines A and B must share producing the last widget to finish by 34 mins approx.

If machines cannot share producing, then answer must be 36 mins..right?

Because, there is similiar problem https://gmatclub.com/forum/crew-a-can-b ... 92819.html
in which, there two crews producing cars, but crews work independently and simulatenously

thanks
Intern
Joined: 01 Oct 2016
Posts: 4
Re: Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

25 Feb 2018, 11:13
Always convert everything in terms of rates -
A - 1/4; b = 1/3; C = 1/5
Fastest two - A and B

Overall rate of A and B combined =1/3+1/4 = 7/12 widgets/minutes

So, 7 widgets take 12 mins -
1 widget will take 12/7 mins
so 20 widgets will take - 12/7*20 = 34(approx)
Non-Human User
Joined: 09 Sep 2013
Posts: 13411
Re: Three machines are operating simultaneously and independently at diffe  [#permalink]

### Show Tags

22 Jul 2019, 16:14
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.
_________________
Re: Three machines are operating simultaneously and independently at diffe   [#permalink] 22 Jul 2019, 16:14
Display posts from previous: Sort by