May 27 01:00 AM PDT  11:59 PM PDT All GMAT Club Tests are free and open on May 27th for Memorial Day! May 27 10:00 PM PDT  11:00 PM PDT Special savings are here for Magoosh GMAT Prep! Even better  save 20% on the plan of your choice, now through midnight on Tuesday, 5/27 May 30 10:00 PM PDT  11:00 PM PDT Application deadlines are just around the corner, so now’s the time to start studying for the GMAT! Start today and save 25% on your GMAT prep. Valid until May 30th. Jun 01 07:00 AM PDT  09:00 AM PDT Learn reading strategies that can help even nonvoracious reader to master GMAT RC Jun 02 07:00 AM PDT  09:00 AM PDT Get personalized insights and an accurate assessment of your current quant score to achieve your Target Quant Score.
Author 
Message 
TAGS:

Hide Tags

Manager
Joined: 03 Aug 2010
Posts: 92
GMAT Date: 08082011

A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
28 Mar 2011, 20:19
Question Stats:
83% (01:29) correct 17% (01:30) wrong based on 63 sessions
HideShow timer Statistics
A box contains either blue or red flags. The total number of flags in the box is an even number. A group of children are asked to pick up two flags each. If all the flags are used up in the process such that 60% of the children have blue flags, and 55% have red flags, what percentage of children have flags of both the colors? A) 5% B) 10% C) 15% D) 20% E) It can not be determined
Official Answer and Stats are available only to registered users. Register/ Login.



Director
Status: Impossible is not a fact. It's an opinion. It's a dare. Impossible is nothing.
Affiliations: University of Chicago Booth School of Business
Joined: 03 Feb 2011
Posts: 709

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
28 Mar 2011, 20:33
60+55=115% hence the overlap is 115100=15% answer C
Posted from my mobile device



Retired Moderator
Joined: 20 Dec 2010
Posts: 1772

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
28 Mar 2011, 21:08
Yalephd wrote: A box contains either blue or red flags. The total number of flags in the box is an even number. A group of children are asked to pick up two flags each. If all the flags are used up in the process such that 60% of the children have blue flags, and 55% have red flags, what percentage of children have flags of both the colors?
A) 5% B) 10% C) 15% D) 20% E) It can not be determined
Is is just me or is this question flawed? Why do think that this question is flawed? Let there be 100 childrenNumber of children with Blue Flag \(= n(B) = 60\) Number of children with Red Flag \(= n(R) = 55\) Number of children with either Red or Blue Flag \(= n(R \cup B) = 100\) Number of children with both Red & Blue Flag \(= n(R \cap B) = ?\) \(n(R \cup B) = n(B) + n(R)  n(R \cap B)\) \(n(R \cap B) = n(B) + n(R)  n(R \cup B)\) \(n(R \cap B) = 60 + 55  100 = 15\) Ans: "C"
_________________



Manager
Joined: 03 Aug 2010
Posts: 92
GMAT Date: 08082011

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
29 Mar 2011, 05:24
I didn't read the question correctly. At first I didn't think that there had to be any overlap, but now that I see that 60% + 55% is greater than 100%, and there has to be overlap. I was thinking of 60 and 55 as real numbers and not as percents. This is now a very easy question in hingsight. Thanks, fluke and gmat1220 fluke wrote: Yalephd wrote: A box contains either blue or red flags. The total number of flags in the box is an even number. A group of children are asked to pick up two flags each. If all the flags are used up in the process such that 60% of the children have blue flags, and 55% have red flags, what percentage of children have flags of both the colors?
A) 5% B) 10% C) 15% D) 20% E) It can not be determined
Is is just me or is this question flawed? Why do think that this question is flawed? Let there be 100 childrenNumber of children with Blue Flag \(= n(B) = 60\) Number of children with Red Flag \(= n(R) = 55\) Number of children with either Red or Blue Flag \(= n(R \cup B) = 100\) Number of children with both Red & Blue Flag \(= n(R \cap B) = ?\) \(n(R \cup B) = n(B) + n(R)  n(R \cap B)\) \(n(R \cap B) = n(B) + n(R)  n(R \cup B)\) \(n(R \cap B) = 60 + 55  100 = 15\) Ans: "C"



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 9246
Location: Pune, India

A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
29 Mar 2011, 18:42
Yalephd wrote: A box contains either blue or red flags. The total number of flags in the box is an even number. A group of children are asked to pick up two flags each. If all the flags are used up in the process such that 60% of the children have blue flags, and 55% have red flags, what percentage of children have flags of both the colors?
A) 5% B) 10% C) 15% D) 20% E) It can not be determined
Is is just me or is this question flawed? When I read this question, I double checked to ensure that it actually is as simple as it seemed. It wasn't a probability question at all (even though, when I started reading it, it looked like a probability question) It was straight forward overlapping sets. The 'number of flags is an even number' is just there to distract you. If each child picked 2 flags and the box got emptied, the number of flag has to be an even number! This does happen quite often in GMAT. The basic concepts remain the same but the presentation changes a little pumping the level of the question up by 50100 points.
_________________
Karishma Veritas Prep GMAT Instructor
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Veritas Prep GMAT Instructor
Joined: 16 Oct 2010
Posts: 9246
Location: Pune, India

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
30 Mar 2011, 13:23
Yalephd wrote: Karishma, that's what threw me off, too. I was confused between approaching this as probability question versus as an overlapping sets problem. Thanks for posting Brian's post. Brian is awesome. I also just took a course with David Newland.
Yes, it does start off as a prob question would but it changes tracks mid way. Anyway, all for the better since it turns out to be on sets which are generally straight forward (GMAT context) I have heard some very good things about David though I haven't got a chance to meet him yet. I have met Brian a couple of times (He is a Michigan guy too!) and he is hilarious. It was fun talking to him and he loves telling these stories, all of them with a lesson for GMAT! I am sure his classes are fun too.
_________________
Karishma Veritas Prep GMAT Instructor
Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >



Manager
Joined: 20 Nov 2010
Posts: 139

A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 03:13
A box contains either blue or red flags. The total number of flags in the box is an even number. A group of children are asked to pick up two flags each. If all the flags are used up in the process such that 60% of the children have blue flags, and 55% have red flags, what percentage of children have flags of both the colors? A) 5% B) 10% C) 15% D) 20% E) It can not be determined
_________________



Intern
Joined: 27 Jul 2011
Posts: 20

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 03:31
The ans is C = 15%
Solution: let the total number of flags be 100(even number)
let the total number of 'blue' flags alone be 'a' let the total number of 'red' flags alone be 'b' let the total number of 'both' flags be 'c'
We have given, total number of blue flags = 60% = 60 = a+c total number of red flags=55%=55=b+c total number of flags = a+b+c=100 (since all the flage have been utlized)
So, substituting for c in the third equation, we have, 60c+c+55c=100 c=15
Option C.
If the above solution looks a bit confusing, try to interpret using Venn diagram. The picture will be more clear.



Manager
Joined: 19 Jul 2011
Posts: 91
Concentration: Finance, Economics
GPA: 3.9

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 03:33
Question is about overlapping sets 60 + 55 = 115 100 = 15 C
_________________
Show Thanks to fellow members with Kudos its shows your appreciation and its free



Senior Manager
Joined: 03 Mar 2010
Posts: 372

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 03:40
+1 for C. I have a question though. How does below statement affect the solution? catfreak wrote: The total number of flags in the box is an even number.
_________________
My dad once said to me: Son, nothing succeeds like success.



Manager
Joined: 19 Jul 2011
Posts: 91
Concentration: Finance, Economics
GPA: 3.9

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 03:48
It has no effect, it is simply there to complicate the answer adding another layer to the problem and thus increasing the difficulty.
_________________
Show Thanks to fellow members with Kudos its shows your appreciation and its free



Manager
Joined: 20 Nov 2010
Posts: 139

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 07:44
I posted this problem because i have a doubt. Since its not mentioned in the problem that every children got two flags each instead its mentioned that all the flags are used in the process so how can we calculate the %age of children who got flags of both colors. What i want to say is that there might be children who didn't get any flags and we don't know their number.
_________________



Manager
Joined: 20 Nov 2010
Posts: 139

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
Updated on: 20 Aug 2011, 07:49
This has an effect on the solution as each of the children is supposed to pick two flags and every children will have two flags in case the number of flags are even. In other words, it is to ensure that there is no child with just one flag. jamifahad wrote: +1 for C. I have a question though. How does below statement affect the solution? catfreak wrote: The total number of flags in the box is an even number.
_________________
Originally posted by catfreak on 20 Aug 2011, 07:46.
Last edited by catfreak on 20 Aug 2011, 07:49, edited 1 time in total.



Manager
Joined: 20 Nov 2010
Posts: 139

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 07:48
Its total number of children with blue flags and not total number of flags. You might want to reread the question. vishal4584 wrote: The ans is C = 15%
Solution: let the total number of flags be 100(even number)
let the total number of 'blue' flags alone be 'a' let the total number of 'red' flags alone be 'b' let the total number of 'both' flags be 'c'
We have given, total number of blue flags = 60% = 60 = a+c total number of red flags=55%=55=b+c total number of flags = a+b+c=100 (since all the flage have been utlized)
So, substituting for c in the third equation, we have, 60c+c+55c=100 c=15
Option C.
If the above solution looks a bit confusing, try to interpret using Venn diagram. The picture will be more clear.
_________________



Director
Joined: 01 Feb 2011
Posts: 646

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
20 Aug 2011, 12:23
= 60+55100
= 15%
Answer is C.



Director
Joined: 27 May 2012
Posts: 787

Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
Show Tags
13 Sep 2018, 06:45
Yalephd wrote: A box contains either blue or red flags. The total number of flags in the box is an even number. A group of children are asked to pick up two flags each. If all the flags are used up in the process such that 60% of the children have blue flags, and 55% have red flags, what percentage of children have flags of both the colors?
A) 5% B) 10% C) 15% D) 20% E) It can not be determined Dear Moderator, Please untag probability. Thank you.
_________________




Re: A box contains either blue or red flags. The total number of flags in
[#permalink]
13 Sep 2018, 06:45






