It is currently 19 Oct 2017, 08:01

STARTING SOON:

Live Chat with Cornell Adcoms in Main Chat Room  |  R1 Interview Invites: MIT Sloan Chat  |  UCLA Anderson Chat  |  Duke Fuqua Chat (EA Decisions)


Close

GMAT Club Daily Prep

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.

Close

Request Expert Reply

Confirm Cancel

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

The waiter at an expensive restaurant has noticed that 60%

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:

Hide Tags

3 KUDOS received
Intern
Intern
User avatar
Joined: 01 Apr 2013
Posts: 23

Kudos [?]: 66 [3], given: 9

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

Show Tags

New post 03 Apr 2013, 18:06
3
This post received
KUDOS
14
This post was
BOOKMARKED
00:00
A
B
C
D
E

Difficulty:

  85% (hard)

Question Stats:

52% (01:31) correct 48% (01:12) wrong based on 562 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?

A. 20%
B. 25%
C. 40%
D. 60%
E. 75%
[Reveal] Spoiler: OA

_________________

The Kudo, please :)


Last edited by Bunuel on 04 Apr 2013, 03:28, edited 1 time in total.
Renamed the topic and edited the question.

Kudos [?]: 66 [3], given: 9

Verbal Forum Moderator
Verbal Forum Moderator
User avatar
Joined: 10 Oct 2012
Posts: 627

Kudos [?]: 1355 [0], given: 136

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

Show Tags

New post 03 Apr 2013, 21:27
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.

B.
_________________

All that is equal and not-Deep Dive In-equality

Hit and Trial for Integral Solutions

Kudos [?]: 1355 [0], given: 136

Expert Post
11 KUDOS received
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41893

Kudos [?]: 128861 [11], given: 12183

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

Show Tags

New post 04 Apr 2013, 03:46
11
This post received
KUDOS
Expert's post
6
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:

Image

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.

Answer: B.

Hope it's clear.

[Reveal] Spoiler:
Attachment:
Coffee and Dessert.png
Coffee and Dessert.png [ 3.79 KiB | Viewed 13805 times ]

_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 128861 [11], given: 12183

Director
Director
avatar
Joined: 03 Aug 2012
Posts: 899

Kudos [?]: 886 [0], given: 322

Concentration: General Management, General Management
GMAT 1: 630 Q47 V29
GMAT 2: 680 Q50 V32
GPA: 3.7
WE: Information Technology (Investment Banking)
Premium Member
Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

New post 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
2set.JPG [ 14 KiB | Viewed 11645 times ]


_________________

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

Kudos [?]: 886 [0], given: 322

Senior Manager
Senior Manager
avatar
Joined: 10 Jul 2013
Posts: 330

Kudos [?]: 419 [0], given: 102

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

Show Tags

New post 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 %
_________________

Asif vai.....

Kudos [?]: 419 [0], given: 102

Manager
Manager
avatar
Joined: 25 Oct 2013
Posts: 169

Kudos [?]: 70 [0], given: 56

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

Show Tags

New post 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%.
_________________

Click on Kudos if you liked the post!

Practice makes Perfect.

Kudos [?]: 70 [0], given: 56

Manager
Manager
User avatar
Joined: 18 Aug 2014
Posts: 130

Kudos [?]: 77 [0], given: 36

Location: Hong Kong
Schools: Mannheim
Re: The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

New post 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

Kudos [?]: 77 [0], given: 36

GMAT Club Legend
GMAT Club Legend
User avatar
Joined: 09 Sep 2013
Posts: 16670

Kudos [?]: 273 [0], given: 0

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

Show Tags

New post 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.
_________________

GMAT Books | GMAT Club Tests | Best Prices on GMAT Courses | GMAT Mobile App | Math Resources | Verbal Resources

Kudos [?]: 273 [0], given: 0

Director
Director
avatar
G
Joined: 07 Dec 2014
Posts: 812

Kudos [?]: 247 [0], given: 12

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

Show Tags

New post 13 Apr 2016, 18:52
let total couples=100
let d=couples who order dessert
d-60=.2d
d=75 couples
100-75=25 couples who don't order dessert
25/100=25%

Kudos [?]: 247 [0], given: 12

Manager
Manager
User avatar
B
Joined: 30 Dec 2015
Posts: 90

Kudos [?]: 20 [0], given: 153

GPA: 3.92
WE: Engineering (Aerospace and Defense)
The waiter at an expensive restaurant has noticed that 60% [#permalink]

Show Tags

New post 08 Oct 2016, 12:50
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%


60% order (C+D) i.e Both = 60% of Total
20% of D is without C; i.e. 80% of D also orders C
80% of D = Both
80% of D = 60% of Total
\(\frac{D}{Total} =\frac{60}{80} = \frac{3}{4}\)
Hence, \(\frac{C}{Total} = \frac{1}{4}\) = 25%
_________________

If you analyze enough data, you can predict the future.....its calculating probability, nothing more!

Kudos [?]: 20 [0], given: 153

SVP
SVP
User avatar
B
Joined: 05 Jul 2006
Posts: 1750

Kudos [?]: 430 [0], given: 49

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

Show Tags

New post 24 Dec 2016, 13:28
Bunuel wrote:
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
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.

Answer: B.

Hope it's clear.


what about (Neither) those who didnt order coffee nor desert

Kudos [?]: 430 [0], given: 49

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41893

Kudos [?]: 128861 [0], given: 12183

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

Show Tags

New post 25 Dec 2016, 01:53
yezz wrote:
Bunuel wrote:
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:

Image

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.

Answer: B.

Hope it's clear.


what about (Neither) those who didnt order coffee nor desert


To get the probability that the next couple will not order dessert we need the percentage of those who do not order dessert which is 25. Those 25% include Coffee/No Dessert and No Coffee/No Dessert (Neither).
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 128861 [0], given: 12183

Intern
Intern
avatar
Joined: 10 Jan 2017
Posts: 1

Kudos [?]: [0], given: 0

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

Show Tags

New post 07 Mar 2017, 08:50
Please help me to understand why is the equation is 60+0.2x = x.
Why shouldn't it be solved as
60 + 20 = x.

Posted from my mobile device

Kudos [?]: [0], given: 0

Expert Post
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 41893

Kudos [?]: 128861 [0], given: 12183

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

Show Tags

New post 07 Mar 2017, 09:20
Nikita16 wrote:
Please help me to understand why is the equation is 60+0.2x = x.
Why shouldn't it be solved as
60 + 20 = x.

Posted from my mobile device


We are given that 20% of the couples who order dessert don't order coffee. We denoted those who order dessert by x, thus those who order dessert but don't order coffee is 20% of that, which is 0.2x.
_________________

New to the Math Forum?
Please read this: Ultimate GMAT Quantitative Megathread | All You Need for Quant | PLEASE READ AND FOLLOW: 12 Rules for Posting!!!

Resources:
GMAT Math Book | Triangles | Polygons | Coordinate Geometry | Factorials | Circles | Number Theory | Remainders; 8. Overlapping Sets | PDF of Math Book; 10. Remainders | GMAT Prep Software Analysis | SEVEN SAMURAI OF 2012 (BEST DISCUSSIONS) | Tricky questions from previous years.

Collection of Questions:
PS: 1. Tough and Tricky questions; 2. Hard questions; 3. Hard questions part 2; 4. Standard deviation; 5. Tough Problem Solving Questions With Solutions; 6. Probability and Combinations Questions With Solutions; 7 Tough and tricky exponents and roots questions; 8 12 Easy Pieces (or not?); 9 Bakers' Dozen; 10 Algebra set. ,11 Mixed Questions, 12 Fresh Meat

DS: 1. DS tough questions; 2. DS tough questions part 2; 3. DS tough questions part 3; 4. DS Standard deviation; 5. Inequalities; 6. 700+ GMAT Data Sufficiency Questions With Explanations; 7 Tough and tricky exponents and roots questions; 8 The Discreet Charm of the DS; 9 Devil's Dozen!!!; 10 Number Properties set., 11 New DS set.


What are GMAT Club Tests?
Extra-hard Quant Tests with Brilliant Analytics

Kudos [?]: 128861 [0], given: 12183

Re: The waiter at an expensive restaurant has noticed that 60%   [#permalink] 07 Mar 2017, 09:20
Display posts from previous: Sort by

The waiter at an expensive restaurant has noticed that 60%

  new topic post reply Question banks Downloads My Bookmarks Reviews Important topics  


GMAT Club MBA Forum Home| About| Terms and Conditions| GMAT Club Rules| Contact| Sitemap

Powered by phpBB © phpBB Group | Emoji artwork provided by EmojiOne

Kindly note that the GMAT® test is a registered trademark of the Graduate Management Admission Council®, and this site has neither been reviewed nor endorsed by GMAC®.