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

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

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New post 11 Mar 2016, 11:23
Bunuel wrote:
SOLUTION

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.

Answer: C.


Are we assuming that there are only 2 things to order- Coffee and dessert and everyone made a choice from these 2 things only... Implying that the sum total of coffee and non-coffee takers = 100%?

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

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New post 27 Nov 2016, 18:01
ts30 wrote:
Bunuel wrote:
SOLUTION

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.

Answer: C.


Are we assuming that there are only 2 things to order- Coffee and dessert and everyone made a choice from these 2 things only... Implying that the sum total of coffee and non-coffee takers = 100%?


I have the same doubt. Bunuel, how do we deduce that there isn't a category of people who haven't ordered anything?
Attachments

File comment: Bunuel, this attached file is my interpretation, although I'm still not clear on how the set of people who don't order coffee or dessert doesn't affect the solution
QR2-DS-116.PNG
QR2-DS-116.PNG [ 20.43 KiB | Viewed 906 times ]


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Last edited by herbgatherer on 28 Nov 2016, 09:43, edited 1 time in total.

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

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New post 28 Nov 2016, 01:34
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herbgatherer wrote:
ts30 wrote:
Bunuel wrote:
SOLUTION

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.

Answer: C.


Are we assuming that there are only 2 things to order- Coffee and dessert and everyone made a choice from these 2 things only... Implying that the sum total of coffee and non-coffee takers = 100%?


I have the same doubt. Bunuel, how do we deduce that there isn't a category of people who haven't ordered anything?


We are not assuming that but the number of people who ordered neither coffee or desert does not play any part in the solution.
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Re: If 75 percent of the guests at a certain banquet ordered dessert, what [#permalink]

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New post 12 Sep 2017, 06:12
Bunuel wrote:
SOLUTION

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.

Answer: C.

It is really clear. Thanks!

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Re: If 75 percent of the guests at a certain banquet ordered dessert, what   [#permalink] 12 Sep 2017, 06:12

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