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# If 75 percent of the guests at a certain banquet ordered dessert, what

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Manager
Joined: 13 Aug 2009
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If 75 percent of the guests at a certain banquet ordered dessert, what  [#permalink]

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20 Aug 2010, 10:30
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Difficulty:

45% (medium)

Question Stats:

65% (01:46) correct 35% (00:30) wrong based on 23 sessions

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If 75 percent of the guests at a certain banquet ordered dessert, what percent of the guests ordered coffee?

(1) 60 percent of the guests who ordered dessert also ordered coffee.
(2) 90 percent of the guests who ordered coffee also ordered dessert.

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Intern
Joined: 15 Aug 2010
Posts: 20
Location: Mumbai
Schools: Class of 2008, IIM Ahmedabad
Re: If 75 percent of the guests at a certain banquet ordered dessert, what  [#permalink]

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20 Aug 2010, 12:55
Hi,

Let total guests be 1000.

# of people who ordered dessert = 750

Statement 1:

# of people who ordered coffee amongst dessert guys - 60% of 750 = 450

# of people who ordered coffee amongst the non - dessert guys - Do not know.

Hence, insufficient.

Statement 2:

90% of coffee drinkers ordered dessert. But, the 750 dessert guys could include people who did not order coffee in the first place. We have no way of knowing this split.

Hence, insufficient.

Statement 1 and 2:

If x is the # of coffee drinkers,

60% of 750 = 90% of x - We really do not want to evaluate x - As long as we realize that x can be calculable, we can conclude that both statements together are sufficient.

Hope this helps. Thanks.
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Naveenan Ramachandran
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Re: If 75 percent of the guests at a certain banquet ordered dessert, what  [#permalink]

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20 Aug 2010, 21:20
I setup up a table, with column A coffee drinks, column B no coffee; row 1 dessert, row 2 no dessert

:::::::::::::: Coffee//No Coffee//Total
Dessert...........?...........?.............75
No Dessert......?...........?............. 25
Total..............?..........?..............100

For statement 1, if we assume there are 100 people at the banquet:
We take 60% of 75:

:::::::::::::: Coffee//No Coffee//Total
Dessert...........45...........30.............75
No Dessert......?...........?............. 25
Total..............?..........?..............100

For statement 2: You can pick any almost multiple of 10 for total coffee drinkers, and the chart would still

:::::::::::::: Coffee//No Coffee//Total
Dessert.........27/9.........?............75
No Dessert......3/1........ ?............ 25
Total............30/10.......?............100

However, if you have both info, and you know what that top left corner is, you can figure out what the bottom left no dessert is. Hope this helps, please give kudos for my really graphic intensive tables
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Intern
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Re: If 75 percent of the guests at a certain banquet ordered dessert, what  [#permalink]

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03 Sep 2010, 00:30
raghavs wrote:
IF 75% of guest at a certain banquet ordered dessert,what percent of guest ordered coffee?

1)60%of the guest who ordered dessert also ordered coffee.

2)90%of the guest who ordered coffee also ordered dessert.

I can able to understand 1 'st stmt but cant able to figure the 2 stmt..Solution in numbers will really help me out.

OA-C

What about the % of people who order neither coffee nor dessert? Is it right to assume that guests ordered only coffee and desert unless mentioned? IMO E as we don't know the % of guests who ordered neither.
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Math Expert
Joined: 02 Sep 2009
Posts: 55150
Re: If 75 percent of the guests at a certain banquet ordered dessert, what  [#permalink]

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14 Aug 2017, 08:42
If 75 percent of the guests at a certain banquet ordered dessert, what percent of the guests ordered coffee?

Assume there were 100 guests on the banquet. So we have that 75 of them ordered dessert.

(1) 60 percent of the guests who ordered dessert also ordered coffee --> 0.6*75=45 guests ordered both dessert AND coffee, but we still don't know how many guests ordered coffee. Not sufficient.

(2) 90 percent of the guests who ordered coffee also ordered dessert --> 0.9*(coffee) # of guests who ordered both dessert AND coffee. Not sufficient.

(1)+(2) From (1) # of guests who ordered both dessert AND coffee is 45 and from (2) 0.9*(coffee)=45 --> (coffee)=50. Sufficient.

OPEN DISCUSSION OF THIS QUESTION IS HERE: http://gmatclub.com/forum/if-75-percent ... 68096.html

--== Message from the GMAT Club Team ==--

THERE IS LIKELY A BETTER DISCUSSION OF THIS EXACT QUESTION.
This discussion does not meet community quality standards. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.

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Re: If 75 percent of the guests at a certain banquet ordered dessert, what   [#permalink] 14 Aug 2017, 08:42
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