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# At a two-day seminar, 90 percent of those registered attende

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VP
Joined: 06 Jun 2004
Posts: 1053
Location: CA
At a two-day seminar, 90 percent of those registered attende [#permalink]

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17 Dec 2005, 23:41
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68% (02:05) correct 32% (01:05) wrong based on 572 sessions

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At a two-day seminar, 90 percent of those registered attended the seminar on the first day. What percent of those registered did not attend the seminar on either day?

(1) A total of 1,000 people registered for the two-day seminar.

(2) Of those registered, 80 percent attended the seminar on the second day.
[Reveal] Spoiler: OA
Manager
Joined: 12 Nov 2005
Posts: 78
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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18 Dec 2005, 11:30
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At a two day seminar, 90% of those registered attended the seminar on the first day. What percent of those registered did not attend the seminar on either day?

(1) A total of 1,000 people registered for the two-day seminar
(2) Of those registered, 80% attended the seminar on the 2nd day

Main Stem: 90% attended on First Day

Statement I:
1000 Registered....We dont know how many attended on Second Day And how many attended on both the days......Insufficient

Statement II:
80% on II day; We dont know how many attended on both the days to find the NONE.......Insufficient

Even after combining Statements I & II, we dont get the percentage attended on both the days to calculate the percentage who didnt attend at all....

Intern
Joined: 16 Oct 2005
Posts: 27
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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19 Dec 2005, 12:06
Kishore wrote:
At a two day seminar, 90% of those registered attended the seminar on the first day. What percent of those registered did not attend the seminar on either day?

(1) A total of 1,000 people registered for the two-day seminar
(2) Of those registered, 80% attended the seminar on the 2nd day

Main Stem: 90% attended on First Day

Statement I:
1000 Registered....We dont know how many attended on Second Day And how many attended on both the days......Insufficient

Statement II:
80% on II day; We dont know how many attended on both the days to find the NONE.......Insufficient

Even after combining Statements I & II, we dont get the percentage attended on both the days to calculate the percentage who didnt attend at all....

Wouldn't the answer be C, if we knew that every participant registered had to attend the seminar on both the days?
Senior Manager
Joined: 09 Aug 2005
Posts: 283
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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19 Dec 2005, 13:39
nothing tells us about the intersection

it is possible that 80% of the people on the second day were from 90 % on the first day - answer in that case is 100

But it is also possible that the 10 % who did not attend on he first day attended on the second day

therefore the answer to the question can be 0
GMAT Club Legend
Joined: 07 Jul 2004
Posts: 5043
Location: Singapore
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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20 Dec 2005, 01:24
(1) 1000 people registered: only information we can get is 900 people attended on day 1. Not sufficient.

(2) We do not know how many attended. Not sufficient.

Using both, still not sufficient as we do not know if the 80% comprised of the remaining 10% that did not attend on day1.

Ans: E
Senior Manager
Joined: 15 Apr 2005
Posts: 415
Location: India, Chennai
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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20 Dec 2005, 03:36
TeHCM wrote:
At a two day seminar, 90% of those registered attended the seminar on the first day. What percent of those registered did not attend the seminar on either day?

(1) A total of 1,000 people registered for the two-day seminar
(2) Of those registered, 80% attended the seminar on the 2nd day

Stmt1 : Nothing is known about the second day. so insuff.
Stmt2: Number of people registered is unknown so insuff.
Combined: % of people who attended on both days is not given. So insuff.

Hence E.
Senior Manager
Joined: 11 Nov 2005
Posts: 328
Location: London
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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20 Dec 2005, 16:44
E.

not possible to determine unless we know the % of registered who attended the seminar both the days.
Manager
Joined: 09 Feb 2006
Posts: 129
Location: New York, NY
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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13 Apr 2006, 16:30
The answer is E. We do not have enough information to solve this problem, because we don't know what percentage the overlap of attendance was between the two days. For example, all 80% that attended the second day also attended the first day. This would result in 10 % of people who didn't attend either day. however, if only 7/8 of the 80% that attended the second day also attended the first day, then you'd have 0% that attended either day. Since we could have multiple values that fulfill this, we cannot answer the question.

Statement 1 is irrelevant.
Manager
Joined: 08 Jul 2007
Posts: 173
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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12 Jul 2007, 13:03
I am getting E on this one.

1) INSUFFICIENT: This tells us that 900 people attended the seminar on the first day. 100 people did not atttend. But we know nothing about day 2.

2) INSUFFICIENT: We don't have any numbers to calculate how many people actually went to the seminar on both days.

Together: We know that 100 people did not attend on day 1 and that 200 people did not attend on day 2. But these could be unique people, so that 0% did not attend the seminars on either day. It could also be that the 100 people who did not attend on day 1 did not attend on day 2. So together insufficient.

A venn diagram would only be useful if we knew something about the overlap, ie how many people who went to the seminar on day 1 that also went on day 2. Since we have nothing on that, I am thinking E.
Director
Joined: 08 Feb 2007
Posts: 610
Location: New Haven, CT
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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12 Jul 2007, 13:16
I would say E, because you don't know how much overlap there is between the first and second days.
Director
Joined: 26 Feb 2006
Posts: 899
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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12 Jul 2007, 13:22
leeye84 wrote:
At a two-day seminar, 90% of those registered attended the seminar on the first day. What percent of those registered did not attend the seminar on either day?

1) A total of 1000 people registered for the two-day seminar.
2) Of those registered, 80% attended the seminar on the second day.

I'm lost on this one. I think Venn Diagram should be used here, but I have no idea how to apply it. Please help. Thanks!

E. We do not know who registered on the first day and who did for the second day. there could be possibility that those registered for the first day did also register for the second day as well. it is also possible that those did not register for the first day also did not register for the second day.

i donot know how to draw a ven diagram on the computer. but if you can, it would clearly help.
Intern
Joined: 18 Aug 2013
Posts: 13

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30 Jun 2014, 10:54
Hi There,

Got the question below, and I am not sure if my approach is correct.
Question is attached.

Here is my solution:
1) Insufficient
2) Insufficient
Together: --> to solve this together we need to know whether the 90% includes both days or just one. Likewise for 80%. It looks like both of them would include both days but we cannot assume. I guess because of that both of these are insuffiecient? Not sure what the real reason is. Hoping that someone can help me out.

Thanks,

Yela
Attachments

Q1_sets.png [ 21.39 KiB | Viewed 10861 times ]

Math Expert
Joined: 02 Sep 2009
Posts: 39626
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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30 Jun 2014, 11:06
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Yela wrote:
Hi There,

Got the question below, and I am not sure if my approach is correct.
Question is attached.

Here is my solution:
1) Insufficient
2) Insufficient
Together: --> to solve this together we need to know whether the 90% includes both days or just one. Likewise for 80%. It looks like both of them would include both days but we cannot assume. I guess because of that both of these are insuffiecient? Not sure what the real reason is. Hoping that someone can help me out.

Thanks,

Yela

Merging similar topics. Please refer to the discussion above and ask if anything remains unclear.

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Posts: 15939
Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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12 Jul 2015, 13:30
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Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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31 Jul 2016, 16:08
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).

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Re: At a two-day seminar, 90 percent of those registered attende [#permalink]

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31 Jan 2017, 18:20
The information from the original problem plus statement (1) give you the first circle (900). Insufficient to solve for Neither.
The information from the original problem plus statement (2) give you the second circle (800). Also Insufficient to solve for Neither.

Together, you still have no idea how many individuals addended Both days. Since the proper formula for such a situation is
Total = Group 1 + Group 2 - Both + Neither, in our case we have
1000 = 900 + 800 - Both + Neither.
Since we are still left with two variables (B and N), the correct answer is E.
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Anaira Mitch

Re: At a two-day seminar, 90 percent of those registered attende   [#permalink] 31 Jan 2017, 18:20
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