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A certain oneday seminar consisted of a morning session and [#permalink]
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A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only. (1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session
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Last edited by Bunuel on 06 Sep 2012, 02:53, edited 1 time in total.
Edited the question.



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Re: One day seminar [#permalink]
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A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only. (1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session (1) 3/4 of 128 is 96. So we know that 96 people attended both seminars. If you draw Venn diagram you'll see that 96 is the intersection of the people who attended morning session and the evening session. This only tells that minimum # of people for the morning session is 96. Morning only could be from 0 to 32. Not sufficient. (2) 7/8 of the people attended the after noon session=112 people. This directly tells that 112 attended after noon session, as each of the 128 people attending the seminar attended at least one of the two sessions hence rest of the people 16, must have been attending the morning session and not attending the evening, which IS only morning session attendant #. Again on Venn diagram 112 would be: only afternoon + intersection of morning and afternoon, so the third part which is morning only would be: total(Afternoon and intersection)=128112=16. Answer: B. P.S. You can attach the file directly to the question, so that everyone see it on the page.
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Re: One day seminar [#permalink]
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16 Aug 2011, 11:23
Bunuel wrote: A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only. (1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session
(1) 3/4 of 128 is 96. So we know that 96 people attended both seminars. If you draw Venn diagram you'll see that 96 is the intersection of the people who attended morning session and the evening session. This only tells that minimum # of people for the morning session is 96. Morning only could be from 0 to 32. Not sufficient.
(2) 7/8 of the people attended the after noon session=112 people. This directly tells that 112 attended after noon session, as each of the 128 people attending the seminar attended at least one of the two sessions hence rest of the people 16, must have been attending the morning session and not attending the evening, which IS only morning session attendant #.
Again on Venn diagram 112 would be: only afternoon + intersection of morning and afternoon, so the third part which is morning only would be: total(Afternoon and intersection)=128102=26.
Answer: B.
P.S. You can attach the file directly to the question, so that everyone see it on the page. Dear bunuel with all respects here is my doubt here is the method to cross check the answer in gmat both option do not contradict (i hope i am correct) according to A 3/4th = 96 people attended both session (morning and afternoon both) and ccording to B 16 (1/8th) people attended morning session now how come both the options are telling different no of people in morning session one more thing what would be the answer if the question were how many of the people attended the morning session [highlight]only omitted[/highlight]PS: had [only] not been in the question no one would have even posted this
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Re: One day seminar [#permalink]
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16 Aug 2011, 12:03
fluke wrote: Warlock007 wrote: Dear bunuel with all respects here is my doubt
here is the method to cross check the answer in gmat both option do not contradict (i hope i am correct). Yes, that's true.
according to A 3/4th = 96 people attended both session (morning and afternoon both) and according to B 16 (1/8th) people attended morning session. Morning session ONLY.
now how come both the options are telling different no of people in morning session. Well!!! Statement 1 is not telling us much about the morning session, except that at least 96 people were there for the morning session. St1 and St2 are telling two different things and both are correct and nonconflicting.
one more thing what would be the answer if the question were how many of the people attended the morning session [highlight]only omitted[/highlight] "C" would be the answer in that case.
PS: had [only] not been in the question no one would have even posted this Dear Fluke were "only" not there then B would have been a straight away answer (why would we need St A)
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Re: One day seminar [#permalink]
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Warlock007 wrote: Dear Fluke were "only" not there then B would have been a straight away answer (why would we need St A) Actually, just the reverse would be correct. Please see the attached picture. Attachment:
Seminar_Morning_Afternoon.JPG [ 9.91 KiB  Viewed 19205 times ]
Morning Session Only = Grey Color = M Both (Morning Session+Afternoon) = Orange Color = M&A Afternoon Session Only = Yellow Color = A Q: If M+M&A+A=128 M=? St1: M&A=96 Not Sufficient. St2: M&A+A=112 Now, we know M&A+A+M=128 M&A+A=112 So, M=16(Morning Session only) Sufficient. Ans: "B" ****************************************************************************** Now, if the question were: How many people attended morning session, we are asked to find M+M&A St1: M&A=96 Not Sufficient. St2: M&A+A=112 Now, we can't find "M&A+M" using this information and the stem. Not Sufficient. Together: We can find "A" and eventually "M&A+M". Sufficient. Ans: "C"
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Re: One day seminar [#permalink]
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16 Aug 2011, 12:29
fluke wrote: Warlock007 wrote: Dear Fluke were "only" not there then B would have been a straight away answer (why would we need St A) Actually, just the reverse would be correct. Please see the attached picture. Attachment: Seminar_Morning_Afternoon.JPG Morning Session Only = Grey Color = M Both (Morning Session+Afternoon) = Orange Color = M&A Afternoon Session Only = Yellow Color = A Q: If M+M&A+A=128 M=? St1: M&A=96 Not Sufficient. St2: M&A+A=112 Now, we know M&A+A+M=128 M&A+A=112 So, M=16(Morning Session only) Sufficient. Ans: "B" ****************************************************************************** Now, if the question were: How many people attended morning session, we are asked to find M+M&A St1: M&A=96 Not Sufficient. St2: M&A+A=112 Now, we can't find "M&A+M" using this information and the stem. Not Sufficient. Together: We can find "A" and eventually "M&A+M". Sufficient. Ans: "C" Bingooooooooooo thanks a lot fluke
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Re: One day seminar [#permalink]
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17 Aug 2011, 05:20
Very nicely explained Fluke...
B it is..



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Re: One day seminar [#permalink]
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21 Aug 2011, 08:52
M only = M  both ?
1. Not sufficient
both = (3/4)*128 = 96
Total = M + A  both
Mboth = 128 A
we still need to know either M or A to find M only.
2. Sufficient
A = (7/8)*128 = 112 Total = M + A  both
=>Mboth = Total  A = 128112 = 16.
Answer is B. 128 =



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Re: One day seminar [#permalink]
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30 Oct 2013, 13:39
Bunuel wrote: A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only.
(1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session
(1) 3/4 of 128 is 96. So we know that 96 people attended both seminars. If you draw Venn diagram you'll see that 96 is the intersection of the people who attended morning session and the evening session. This only tells that minimum # of people for the morning session is 96. Morning only could be from 0 to 32. Not sufficient.
(2) 7/8 of the people attended the after noon session=112 people. This directly tells that 112 attended after noon session, as each of the 128 people attending the seminar attended at least one of the two sessions hence rest of the people 16, must have been attending the morning session and not attending the evening, which IS only morning session attendant #.
Again on Venn diagram 112 would be: only afternoon + intersection of morning and afternoon, so the third part which is morning only would be: total(Afternoon and intersection)=128102=26.
Answer: B.
P.S. You can attach the file directly to the question, so that everyone see it on the page. Bunuel, Statement 2 says that 7/8 attended the afternoon session (i.e. 112 ppl). From these, we don't know how many attended afternoon only or morning + afternoon, hence how can we say for sure that 16 attended morning only?



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Re: One day seminar [#permalink]
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Skag55 wrote: Bunuel wrote: A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only.
(1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session
(1) 3/4 of 128 is 96. So we know that 96 people attended both seminars. If you draw Venn diagram you'll see that 96 is the intersection of the people who attended morning session and the evening session. This only tells that minimum # of people for the morning session is 96. Morning only could be from 0 to 32. Not sufficient.
(2) 7/8 of the people attended the after noon session=112 people. This directly tells that 112 attended after noon session, as each of the 128 people attending the seminar attended at least one of the two sessions hence rest of the people 16, must have been attending the morning session and not attending the evening, which IS only morning session attendant #.
Again on Venn diagram 112 would be: only afternoon + intersection of morning and afternoon, so the third part which is morning only would be: total(Afternoon and intersection)=128102=26.
Answer: B.
P.S. You can attach the file directly to the question, so that everyone see it on the page. Bunuel, Statement 2 says that 7/8 attended the afternoon session (i.e. 112 ppl). From these, we don't know how many attended afternoon only or morning + afternoon, hence how can we say for sure that 16 attended morning only? Consider this: we are asked to find how many of the people attended the morning session only. So, we need to find {Morning}  {Both}. Now: {Total} = {Morning} + {Afternoon}  {Both}; {128} = {Morning} + 112  {Both}; {Morning}  {Both} = 16. Does this make sense?
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Re: One day seminar [#permalink]
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31 Oct 2013, 04:43
Bunuel wrote: Skag55 wrote: Bunuel wrote: A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only.
(1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session
(1) 3/4 of 128 is 96. So we know that 96 people attended both seminars. If you draw Venn diagram you'll see that 96 is the intersection of the people who attended morning session and the evening session. This only tells that minimum # of people for the morning session is 96. Morning only could be from 0 to 32. Not sufficient.
(2) 7/8 of the people attended the after noon session=112 people. This directly tells that 112 attended after noon session, as each of the 128 people attending the seminar attended at least one of the two sessions hence rest of the people 16, must have been attending the morning session and not attending the evening, which IS only morning session attendant #.
Again on Venn diagram 112 would be: only afternoon + intersection of morning and afternoon, so the third part which is morning only would be: total(Afternoon and intersection)=128102=26.
Answer: B.
P.S. You can attach the file directly to the question, so that everyone see it on the page. Bunuel, Statement 2 says that 7/8 attended the afternoon session (i.e. 112 ppl). From these, we don't know how many attended afternoon only or morning + afternoon, hence how can we say for sure that 16 attended morning only? Consider this: we are asked to find how many of the people attended the morning session only. So, we need to find {Morning}  {Both}. Now: {Total} = {Morning} + {Afternoon}  {Both}; {128} = {Morning} + 112  {Both}; {Morning}  {Both} = 16. Does this make sense? "So, we need to find {Morning}  {Both}". I see now, thanks!



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Re: A certain oneday seminar consisted of a morning session and [#permalink]
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02 Nov 2013, 08:52
Bunuel how did u get 102. I did not understand. Can u please explain?



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Re: A certain oneday seminar consisted of a morning session and [#permalink]
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18 May 2015, 09:38
I tried solving this prob. by using double set matrix. Is that a wrong approach for this problem? I got (C) by doing that.



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arkle wrote: I tried solving this prob. by using double set matrix. Is that a wrong approach for this problem? I got (C) by doing that. Hi arkle, The question asks us to find the number of people who attended the morning session only i.e. who attended the morning session but did not attend the afternoon session. Even when using the double set matrix you will get option B as the answer. Please refer the diagram of the matrix below for statementII: We are given that 7/8 of the people attended the afternoon session i.e. number of people who attended afternoon session irrespective of whether they attended morning session or not is 112. Since the total number of people who attended the session is 128, we get the number of people who did not attend the afternoon session as 128  112 = 16. As everyone attended at least one session there were 0 number of people who did not attend any of the session. That leaves us with 16 number of people who did not attend the afternoon session but attended only the morning session which is what the question asks us . Hence stII is sufficient to answer the question. Hope this helps Regards Harsh
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Re: A certain oneday seminar consisted of a morning session and [#permalink]
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18 May 2015, 11:54
thanks so much for this. I thought the question is asking total morning i.e. morningUafternoon+morningUnoAfternoon => 96+16. That's why I selected (C)



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Re: A certain oneday seminar consisted of a morning session and [#permalink]
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06 Jan 2016, 14:12
adarsh12345 wrote: A certain oneday seminar consisted of a morning session and an afternoon session. If each of the 128 people attending the seminar attended at least one of the two sessions, how many of the people attended the morning session only.
(1) 3/4 of the people attended both sessions (2) 7/8 of the people attended the after noon session You can make a 600 questions from this one, using doublematrix + attention to details > attended at least one > means, NEITHER=0 and morning session only > Means morning session BUT not an afternoon session
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