Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

It appears that you are browsing the GMAT Club forum unregistered!

Signing up is free, quick, and confidential.
Join other 500,000 members and get the full benefits of GMAT Club

Registration gives you:

Tests

Take 11 tests and quizzes from GMAT Club and leading GMAT prep companies such as Manhattan GMAT,
Knewton, and others. All are free for GMAT Club members.

Applicant Stats

View detailed applicant stats such as GPA, GMAT score, work experience, location, application
status, and more

Books/Downloads

Download thousands of study notes,
question collections, GMAT Club’s
Grammar and Math books.
All are free!

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

03 Apr 2013, 18:06

2

This post received KUDOS

4

This post was BOOKMARKED

00:00

A

B

C

D

E

Difficulty:

75% (hard)

Question Stats:

52% (02:26) correct
48% (01:08) wrong based on 306 sessions

HideShow timer Statistics

The waiter at an expensive restaurant has noticed that 60% of the couples order dessert and coffee. However, 20% of the couples who order dessert don't order coffee. What is the probability that the next couple the waiter seats will not order dessert?

Re: The waiter at an expensive resturant has noticed [#permalink]

Show Tags

03 Apr 2013, 21:27

Expert's post

Tagger wrote:

The waiter at an expensive resturant has noticed that 60% of the couples order desert and coffee. However, 20% of the couples who order desert dont order coffee. what is the probability that the next couple the waiter seats will not order desert?

A.) 20% B.) 25% C.) 40% D.) 60% E.) 75%

Let the number of people ordering only desert = d, only ordering coffee be c and ordering both be b. Given that , 20 % of (b+d) = d

or 4d = b.

Thus, as b = 60, d = 15. The total number of people not ordering desert = 100-(60+15) = 25.

Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

04 Apr 2013, 03:46

8

This post received KUDOS

Expert's post

1

This post was BOOKMARKED

Tagger wrote:

The waiter at an expensive restaurant has noticed that 60% of the couples order dessert and coffee. However, 20% of the couples who order dessert don't order coffee. What is the probability that the next couple the waiter seats will not order dessert?

A. 20% B. 25% C. 40% D. 60% E. 75%

Probably the best way to solve this question is using the double set matrix, as shown below:

Attachment:

Coffee and Dessert.png [ 3.79 KiB | Viewed 7745 times ]

From above, we have that 60+0.2x=x --> x=75.

Thus, the probability that the next couple will not order dessert (yellow box) is 100-75=25.

Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

17 Aug 2013, 22:25

Solving for X in the figure shown below we will get Couples for deserts as 75% And couples not ordering deserts =100-75=25%

Attachments

2set.JPG [ 14 KiB | Viewed 6559 times ]

_________________

Rgds, TGC! _____________________________________________________________________ I Assisted You => KUDOS Please _____________________________________________________________________________

Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

18 Aug 2013, 16:31

Tagger wrote:

The waiter at an expensive restaurant has noticed that 60% of the couples order dessert and coffee. However, 20% of the couples who order dessert don't order coffee. What is the probability that the next couple the waiter seats will not order dessert?

A. 20% B. 25% C. 40% D. 60% E. 75%

Let, total dessert ordered = T and total couple = 100 From question, 60+20% of T = T or, T = 75 % ordered dessert.

So next couple will not order dessert = 100-75 = 25 % _________________

Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

24 Jan 2014, 06:09

Let total number of couples be 100.

60% order Dessert & Coffee = 60 couples. 20% who order Dessert do not order coffee => 80% who order dessert also order coffee this is given to be 60. Hence total number of couples who order Dessert is 60*100/80 = 75. Number of couples who do NOT order Dessert = 100-75 = 25. The probability that next order will not have dessert is 25%. _________________

Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

13 Feb 2015, 00:24

Tagger wrote:

The waiter at an expensive restaurant has noticed that 60% of the couples order dessert and coffee. However, 20% of the couples who order dessert don't order coffee. What is the probability that the next couple the waiter seats will not order dessert?

A. 20% B. 25% C. 40% D. 60% E. 75%

I solved this pretty fast this way:

60% dessert and coffee --> 40% nothing, dessert, or coffee

Let them be the same probability --> 40% / 3 = 13,333%

40% - 13% = 27% --> Answer has to be around this range --> B is closest

Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

13 Apr 2016, 05:44

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).

Want to see all other topics I dig out? Follow me (click follow button on profile). You will receive a summary of all topics I bump in your profile area as well as via email. _________________

Part 2 of the GMAT: How I tackled the GMAT and improved a disappointing score Apologies for the month gap. I went on vacation and had to finish up a...

Cal Newport is a computer science professor at GeorgeTown University, author, blogger and is obsessed with productivity. He writes on this topic in his popular Study Hacks blog. I was...

So the last couple of weeks have seen a flurry of discussion in our MBA class Whatsapp group around Brexit, the referendum and currency exchange. Most of us believed...