Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 31 Mar 2010
Posts: 128

Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
Updated on: 15 Oct 2014, 11:54
Question Stats:
54% (01:18) correct 46% (01:32) wrong based on 354 sessions
HideShow timer Statistics
Crew A can build a complete car in 20 minutes and Crew B can build a complete car in 25 minutes. If both crews work independently and start at the same time, what is the shortest amount of time it could take for 10 cars to be complete? A. 111 1/9 minutes B. 115 2/5 minutes C. 116 minutes D. 120 minutes E. 125 minutes
Official Answer and Stats are available only to registered users. Register/ Login.
Originally posted by widerangeinput on 17 Apr 2010, 05:27.
Last edited by Bunuel on 15 Oct 2014, 11:54, edited 1 time in total.
Renamed the topic, edited the question and added the OA.



Manager
Joined: 05 Mar 2010
Posts: 182

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
17 Apr 2010, 05:53
IMO D because in 100 min both crew will complete 9 cars (5 by crew A and 4 by crew B) then crew a will finish the 10th car in next 20 min (before crew B which will complete their next care in 25 min, 5 min more than A) Hope this helps
_________________
Success is my Destiny



Manager
Joined: 31 Mar 2010
Posts: 128

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
17 Apr 2010, 06:41
hardnstrong wrote: IMO D
because in 100 min both crew will complete 9 cars (5 by crew A and 4 by crew B) then crew a will finish the 10th car in next 20 min (before crew B which will complete their next care in 25 min, 5 min more than A)
Hope this helps I just overlooked this "independently" clause. Just did the 1/20+1/25 thing... Thank you



CEO
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2657
Location: Malaysia
Concentration: Technology, Entrepreneurship
GMAT 1: 670 Q49 V31 GMAT 2: 710 Q50 V35

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
17 Apr 2010, 12:48
why dont we read it CAREFULLY .....best thing is to read the question again before submitting the ans.
_________________
Fight for your dreams :For all those who fear from Verbal lets give it a fight
Money Saved is the Money Earned
Jo Bole So Nihaal , Sat Shri Akaal
Support GMAT Club by putting a GMAT Club badge on your blog/Facebook
GMAT Club Premium Membership  big benefits and savings
Gmat test review : http://gmatclub.com/forum/670to710alongjourneywithoutdestinationstillhappy141642.html



Manager
Joined: 31 Mar 2010
Posts: 128

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
17 Apr 2010, 12:51
gurpreetsingh wrote: why dont we read it CAREFULLY .....best thing is to read the question again before submitting the ans. exactly



Intern
Joined: 19 Feb 2010
Posts: 5

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
19 Apr 2010, 11:23
please forgive me....but would you mind spelling out why working independently has an effect? Unfortunately I still don't get it.....even if they work independently, aren't at total of 10 cars completed between the two of them? Thanks



Intern
Joined: 19 Feb 2010
Posts: 5

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
19 Apr 2010, 11:24
please forgive me....but would you mind spelling out why working independently has an effect? Unfortunately I still don't get it.....even if they work independently, aren't at total of 10 cars completed between the two of them? Thanks



Manager
Joined: 31 Mar 2010
Posts: 128

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
19 Apr 2010, 11:38
PeterFaulkner wrote: please forgive me....but would you mind spelling out why working independently has an effect? Unfortunately I still don't get it.....even if they work independently, aren't at total of 10 cars completed between the two of them? Thanks welll, A can build a car in 20 minutes and B in 25. So if they both utilize their production capabilities and work on a single car together, this should logically take less than 20 minutes for sure. (Think of it like, A is working on a car and B is helping A at the same time this should definitely take way less then 20 minutes...) mathematically: it's 1/20+1/25=9/100 where it takes 100/9 hours to build a single car. Thus it takes 111 1/9 hours to complete 10 of them. And here you go the guys put this one into the very first choice so that you'll fall into that trap! hope this has been clear and does make sense



Senior Manager
Status: Yeah well whatever.
Joined: 18 Sep 2009
Posts: 328
Location: United States
GMAT 1: 660 Q42 V39 GMAT 2: 730 Q48 V42
GPA: 3.49
WE: Analyst (Insurance)

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
19 Apr 2010, 12:26
I strongly dislike this question. If we’re to assume that rates can be fractional then why can’t the same be assumed for work also? I wonder if the GMAC would put something this ambiguous on the real test.
_________________
He that is in me > he that is in the world.  source 1 John 4:4



Manager
Joined: 05 Mar 2010
Posts: 182

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
20 Apr 2010, 01:46
widerangeinput wrote: Crew A can build a complete car in 20 minutes and Crew B can build a complete car in 25 minutes. If both crews work independently and start at the same time, what is the shortest amount of time it could take for 10 cars to be complete? A. 111 1/9 minutes B. 115 2/5 minutes C. 116 minutes D. 120 minutes E. 125 minutes 800score.com says it is D. I think it should be A Let me know what you think thanks read the question carefully. the red highlighted part. How can you combine when question clearly says they both work independently
_________________
Success is my Destiny



Senior Manager
Status: Yeah well whatever.
Joined: 18 Sep 2009
Posts: 328
Location: United States
GMAT 1: 660 Q42 V39 GMAT 2: 730 Q48 V42
GPA: 3.49
WE: Analyst (Insurance)

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
20 Apr 2010, 04:55
if the question said 10 whole cars then i'd say "okay that makes sense" but even from an accounting perspective inventory is recorded by the percentage of its completion and added up (not that that applies here. i'm just saying that there is nothing that explicitly states that it doesn't apply.)
_________________
He that is in me > he that is in the world.  source 1 John 4:4



VP
Status: There is always something new !!
Affiliations: PMI,QAI Global,eXampleCG
Joined: 08 May 2009
Posts: 1142

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
09 May 2011, 00:16
Good question indeed. Let crew A works for x min and crew B works for y min independently for 10 cars crew A makes 1/20 car/ min and crew B makes 1/25 car / min then, x*(1/20) + y*(1/25) = 10 Taking LCM for 20 and 25 min = 100. Means when x=y = 100 mints each, number of cars = 5+4 = 9. Crew A finishes a car faster than crew B. hence 100 + 20 = 120 will be the time needed for 10 cars.
_________________
Visit  http://www.sustainablesphere.com/ Promote Green Business,Sustainable Living and Green Earth !!



Retired Moderator
Joined: 16 Nov 2010
Posts: 1472
Location: United States (IN)
Concentration: Strategy, Technology

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
10 May 2011, 07:58
A builds 4 cars in 80 min B builds 4 cars in 100 min So A builds another car in another 20 min (i.e total 5 cars) B builds another car in another 25 minutes (i.e, total 5 cars) However, A can build another car in next 20 min (i.e total 6 cars) So total time = 125 min by B, which is > 120 min by A B  4 cars, A  6 cars Answer = D
_________________
Formula of Life > Achievement/Potential = k * Happiness (where k is a constant)
GMAT Club Premium Membership  big benefits and savings



Manager
Joined: 11 Dec 2010
Posts: 108
WE: Consulting (Consulting)

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
10 May 2011, 10:27
Take the one that needs less time i.e. 20 min... 20 min*5 = 100 min So total 9 cars can be made in 100 min (5 from A and 4 from B) So one more car would need 20 more min
So shortest time for 10 cars in 120 min...



Senior Manager
Joined: 28 Jul 2011
Posts: 412
Location: United States
Concentration: International Business, General Management
GPA: 3.86
WE: Accounting (Commercial Banking)

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
30 Oct 2011, 12:15
omg I fell into trap...........interesting question
_________________
+1 Kudos If found helpful..



Manager
Joined: 02 Jul 2012
Posts: 202
Location: India
GPA: 2.6
WE: Information Technology (Consulting)

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
15 Oct 2014, 13:13
widerangeinput wrote: Crew A can build a complete car in 20 minutes and Crew B can build a complete car in 25 minutes. If both crews work independently and start at the same time, what is the shortest amount of time it could take for 10 cars to be complete?
A. 111 1/9 minutes B. 115 2/5 minutes C. 116 minutes D. 120 minutes E. 125 minutes Ha Ha Ha Ha.. Awesome question. Its easy and has a trap. I fell into it. As soon as I read Time taken to complete cars, started solving by Work ratio method... Later on realized my mistake...
_________________
Give KUDOS if the post helps you...



Manager
Joined: 17 Sep 2017
Posts: 61

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
30 Nov 2017, 09:00
I'm not fully clear neither algebra solution nor the shortcut way. Can anyone please elaborate clearly on this question?



Director
Joined: 08 Jun 2015
Posts: 509
Location: India
GMAT 1: 640 Q48 V29 GMAT 2: 700 Q48 V38

Re: Crew A can build a complete car in 20 minutes and Crew B can build a [#permalink]
Show Tags
30 Apr 2018, 06:36
A tricky one indeed !!! Note that the question wants us to find the least number of minutes when the two are working independently. In 100 min Crew A makes 5 and Crew B makes 4 cars. Tenth car will take 20 min for Crew A. Minimum of 120 minutes will be required. Option D it is !!
_________________
" The few , the fearless "




Re: Crew A can build a complete car in 20 minutes and Crew B can build a
[#permalink]
30 Apr 2018, 06:36






