Machine A produces bolts at a uniform rate of 120 every 40 : GMAT Problem Solving (PS)
Check GMAT Club App Tracker for the Latest School Decision Releases http://gmatclub.com/AppTrack

 It is currently 07 Dec 2016, 11:35

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

Machine A produces bolts at a uniform rate of 120 every 40

Author Message
TAGS:

Hide Tags

Manager
Joined: 02 Dec 2012
Posts: 178
Followers: 5

Kudos [?]: 2206 [1] , given: 0

Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

07 Dec 2012, 03:03
1
KUDOS
5
This post was
BOOKMARKED
00:00

Difficulty:

5% (low)

Question Stats:

90% (02:10) correct 10% (01:46) wrong based on 819 sessions

HideShow timer Statistics

Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56
[Reveal] Spoiler: OA
Math Expert
Joined: 02 Sep 2009
Posts: 35912
Followers: 6851

Kudos [?]: 90022 [2] , given: 10402

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

07 Dec 2012, 03:05
2
KUDOS
Expert's post
1
This post was
BOOKMARKED
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56

Machine A produces 120/40=3 bolts per second;
Machine B produces 100/20=5 bolts per second.

Running simultaneously, they produce 3+5=8 bolts per second, thus it will take them 200/8=25 seconds to produce 200 bolts.

_________________
Manager
Joined: 30 Mar 2013
Posts: 137
Followers: 0

Kudos [?]: 39 [0], given: 196

Machine A produces bolts at a uniform rate of 120 [#permalink]

Show Tags

12 Nov 2013, 07:49
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56

why cant i do it this way:
take 1/time taken for each machine to produce 20 bolts: thats (1/60) for A plus (1/100) for B. Then I add them up and take the reciprocal to get total time taken. thats 37.45. so its 37.45 bolts every 20 secs. so that 106.8 seconds for 200 bolts.

whats wrong with what I did?
Senior Manager
Status: busyness school student
Joined: 09 Sep 2013
Posts: 419
Location: United States
Schools: Tepper '16 (M)
GMAT 1: 730 Q52 V37
Followers: 16

Kudos [?]: 294 [0], given: 145

Re: Machine A produces bolts at a uniform rate of 120 [#permalink]

Show Tags

12 Nov 2013, 08:06
Machine A produces 120 bolts every 40 seconds.
How many bolts does Machine A produce every second?
Machine A produces 120/40 = 3 bolts every second.

Machine B produces 100 bolts every 20 seconds.
How many bolts does Machine B produce every second?
Machine B produces 100/20 = 5 bolts every second.

Together, Machine A and Machine B produces 3+5 = 8 bolts every second.

8 bolts / 1 sec = 200 bolts / x sec

Cross multiply, and get 200 = 8x; so, 25 = x.
So it takes 25 seconds to produce 200 bolts, when Machine A and Machine B work together.

Quote:
why cant i do it this way:
take 1/time taken for each machine to produce 20 bolts: thats (1/60) for A plus (1/100) for B. Then I add them up and take the reciprocal to get total time taken. thats 37.45. so its 37.45 bolts every 20 secs. so that 106.8 seconds for 200 bolts.

Unfortunately, I'm having trouble following your logic. It looks like you try to find how much time it takes to produce 20 bolts, but then later try to figure out how many bolts are produced every 20 seconds?
_________________

My review of some of the CAT practice exams
You can usually find me on gmatclub's chat.

Manager
Joined: 30 Mar 2013
Posts: 137
Followers: 0

Kudos [?]: 39 [0], given: 196

Re: Machine A produces bolts at a uniform rate of 120 [#permalink]

Show Tags

12 Nov 2013, 08:23
I apply the simple formula: 1/(time taken by machine A) + 1/(time taken by machine B) = 1/(total time taken by both machines, together. this is now the rate (together). to get total time taken, inverse it. but i see what i did. i started adding the total bolts, thinking thats the time. i see my error, thank you. but the formula mentioned above (in my post) is correct, right?
Math Expert
Joined: 02 Sep 2009
Posts: 35912
Followers: 6851

Kudos [?]: 90022 [0], given: 10402

Re: Machine A produces bolts at a uniform rate of 120 [#permalink]

Show Tags

12 Nov 2013, 09:12
usre123 wrote:
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56

why cant i do it this way:
take 1/time taken for each machine to produce 20 bolts: thats (1/60) for A plus (1/100) for B. Then I add them up and take the reciprocal to get total time taken. thats 37.45. so its 37.45 bolts every 20 secs. so that 106.8 seconds for 200 bolts.

whats wrong with what I did?

Merging similar topics. Please refer to the solution above.

_________________
Manager
Joined: 07 Apr 2014
Posts: 147
Followers: 1

Kudos [?]: 22 [0], given: 81

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

11 Sep 2014, 05:35
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56

Machine A .. 120 in 40 seconds then 3 /sec
machine B .. 100 in 20 seconds then 5/sec

in one sec both can produce 8.

so for 200 , 200/8 = 25
SVP
Status: The Best Or Nothing
Joined: 27 Dec 2012
Posts: 1858
Location: India
Concentration: General Management, Technology
WE: Information Technology (Computer Software)
Followers: 44

Kudos [?]: 1834 [2] , given: 193

Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

30 Sep 2014, 22:16
2
KUDOS
Time required = $$\frac{200}{\frac{120}{40} + \frac{100}{20}} = \frac{200}{8} = 25$$

_________________

Kindly press "+1 Kudos" to appreciate

GMAT Club Legend
Joined: 09 Sep 2013
Posts: 12886
Followers: 561

Kudos [?]: 158 [0], given: 0

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

04 Oct 2015, 10:13
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.
_________________
GMAT Club Legend
Joined: 09 Sep 2013
Posts: 12886
Followers: 561

Kudos [?]: 158 [0], given: 0

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

12 Oct 2016, 02:29
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: 2115
Location: India
GPA: 3.5
Followers: 82

Kudos [?]: 557 [0], given: 311

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

12 Oct 2016, 10:55
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56

Efficiency of machine A = 3 bolts/sec
Efficiency of machine B = 5 bolts/sec

Combined efficiency of the 8 bolts/sec

So, Time required to produce 200 bolts will be $$\frac{200}{8}$$ = 25 seconds...

_________________

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 )

Senior Manager
Status: Founder & CEO
Affiliations: Target Test Prep
Joined: 14 Oct 2015
Posts: 428
Location: United States (CA)
Followers: 13

Kudos [?]: 128 [1] , given: 2

Re: Machine A produces bolts at a uniform rate of 120 every 40 [#permalink]

Show Tags

14 Oct 2016, 04:56
1
KUDOS
Machine A produces bolts at a uniform rate of 120 every 40 seconds, and Machine B produces bolts at a uniform rate of 100 every 20 seconds. If the two machines run simultaneously, how many seconds will it take for them to produce a total of 200 bolts?

(A) 22
(B) 25
(C) 28
(D) 32
(E) 56

We are given that machine A produces bolts at a uniform rate of 120 every 40 seconds. Thus, the rate of Machine A is 120/40 = 3 bolts/second.

We are also given that Machine B produces bolts at a uniform rate of 100 every 20 seconds. Thus, the rate of Machine B is 100/20 = 5 bolts/second.

We need to determine the time it will take to produce 200 bolts when the two machines run simultaneously.

To determine the time to produce 200 bolts, we can use the combined work formula:

Work by Machine A + Work by Machine B = 200 bolts (the total work completed).

Because both machines are working simultaneously, we can say that they both work together for t seconds. We now can express the individual work done by Machine A and by Machine B. We must remember that work = rate x time.

Work done by Machine A = 3t

Work done by Machine B = 5t

3t + 5t = 200

8t = 200

t = 200/8 = 25

_________________

Jeffrey Miller
Scott Woodbury-Stewart
Founder and CEO

Re: Machine A produces bolts at a uniform rate of 120 every 40   [#permalink] 14 Oct 2016, 04:56
Similar topics Replies Last post
Similar
Topics:
Machine–A produces 40% of the total output and Machine-B produces 60% 2 03 Jul 2016, 11:24
6 Two identical machines have the ability to produce both nuts and bolts 7 15 Jun 2015, 23:18
6 Running at the same rate, 8 identical machines can produce 560 papercl 6 27 Feb 2015, 05:01
7 Machines X and Y produce bottles at their respective constant rates. 12 29 Aug 2010, 19:43
13 Machine A produces pencils at a constant rate of 9,000 pencils per hou 12 04 Apr 2007, 16:09
Display posts from previous: Sort by