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A certain one-day seminar consisted of a morning session and

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adarsh12345
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A certain one-day seminar consisted of a morning session and [#permalink] New post   Updated on: 01 Sep 2019, 13:33
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A certain one-day 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 afternoon session
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B

Originally posted by adarsh12345 on 12 Nov 2009, 08:59.
Last edited by MikeScarn on 01 Sep 2019, 13:33, edited 2 times in total.
Edited the question.
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   12 Nov 2009, 09:22
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A certain one-day 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)=128-112=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: A certain one-day seminar consisted of a morning session and [#permalink] New post   16 Aug 2011, 12:24
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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
Seminar_Morning_Afternoon.JPG [ 9.91 KiB | Viewed 86799 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: A certain one-day seminar consisted of a morning session and [#permalink] New post   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 non-conflicting.

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: A certain one-day seminar consisted of a morning session and [#permalink] New post   21 Aug 2011, 08:52
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M only = M - both ?

1. Not sufficient

both = (3/4)*128 = 96

Total = M + A - both

M-both = 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

=>M-both = Total - A = 128-112 = 16.

Answer is B.
128 =
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   30 Oct 2013, 13:39
Bunuel wrote:
A certain one-day 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)=128-102=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: A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Oct 2013, 01:23
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Skag55 wrote:
Bunuel wrote:
A certain one-day 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)=128-102=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: A certain one-day seminar consisted of a morning session and [#permalink] New post   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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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   18 May 2015, 10:58
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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 statement-II:



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 st-II is sufficient to answer the question.

Hope this helps :)

Regards
Harsh
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   23 Jan 2021, 21:48
C-trap problem.

A certain one-day 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
3/4 x 128 = 96 attended both but we don't know how many attended the morning session but NOT the afternoon session as well.
Insufficient

(2) 7/8 of the people attended the afternoon session
7/8 x 128 = 128
This tells us that the number of people who DID NOT attend the afternoon session is 16.

Sufficient.
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   09 Apr 2021, 20:20
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adarsh12345 wrote:
A certain one-day 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 afternoon session


Answer: Option B

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A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 10:21
Hi avigutman - my question is on the MECE groups in this question.

I eventually got the table right, which is below

Attachment:
screenshot 6.jpg
screenshot 6.jpg [ 17.62 KiB | Viewed 10060 times ]


My question is the following however :

a) would you agree - morning and afternoon are MECE groups ?

What I mean is -- I thought the grouping instead was this instead
Attachment:
screenshot 9.jpg
screenshot 9.jpg [ 17.18 KiB | Viewed 10066 times ]


I know that my 2nd table is NOT RIGHT but my question still stands :

-- Afternoon and Morning can be MECE groups, can they not ?
--
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 12:18
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jabhatta2 wrote:
-- Afternoon and Morning can be MECE groups, can they not ?
--

Sure, jabhatta2. If you know that it’s impossible to attend both morning AND afternoon sessions, and if you know that everyone did attend one of them, then by definition they are MECE. If at least one of those conditions is false, then they’re not MECE.

Posted from my mobile device
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A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 13:23
Thanks so Much avigutman ! I think you are saying – my 2nd table above is possible.

Attached is an example of my 2nd table with morning/afternoon vs with boys/girls

Attachment:
screenshot 10 .jpg
screenshot 10 .jpg [ 19.65 KiB | Viewed 9984 times ]


avigutman wrote:
jabhatta2 wrote:
-- Afternoon and Morning can be MECE groups, can they not ?
--

Sure, jabhatta2. If you know that it’s impossible to attend both morning AND afternoon sessions, and if you know that everyone did attend one of them, then by definition they are MECE. If at least one of those conditions is false, then they’re not MECE.


Regarding the yellow – I think you are referring to morning/afternoon specifically in my 2nd table above

Everyone attends either morning/afternoon
Its impossible to attend BOTH morning/afternoon

Both of these are true in regards to table 2 specifically (where morning /afternoon are on the vertical line)

I ask because in the original question -- you can attend morning and afternoon AT the same time.
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 13:57
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jabhatta2 wrote:
I ask because in the original question -- you can attend morning and afternoon AT the same time.

Right, jabhatta2, so in the original question morning and afternoon are not MECE.

Posted from my mobile device
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A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 14:53
avigutman wrote:
jabhatta2 wrote:
I ask because in the original question -- you can attend morning and afternoon AT the same time.

Right, jabhatta2, so in the original question morning and afternoon are not MECE.

Posted from my mobile device


thanks so much avigutman - interesting

afternoon/morning can be MECE / may not be MECE (Depending on the question)

girls/boys I think will always be MECE
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 15:57
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jabhatta2 wrote:
girls/boys I think will always be MECE

That's way too politically charged for me to weigh in on, jabhatta2.
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A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 17:12
avigutman wrote:
jabhatta2 wrote:
girls/boys I think will always be MECE

That's way too politically charged for me to weigh in on, jabhatta2.


Hi avigutman - should have clarified.

I meant in the context of the GMAT - girls/boys are always MECE (in the context of the GMAT)

Obviously, based in Canada - that is not the case.
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Re: A certain one-day seminar consisted of a morning session and [#permalink] New post   31 Jan 2023, 17:29
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jabhatta2 wrote:
I meant in the context of the GMAT - girls/boys are always MECE (in the context of the GMAT)

jabhatta2 Any published official GMAC problems that mention boys and girls do require that we assume that those categories are MECE, yes.
However, I recall hearing around 5 years ago that current and future questions on the test will no longer require that assumption.
So I don't think we'll face that issue going forward. They'll probably just avoid using gender as a category for overlapping sets questions.
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