GMAT Question of the Day - Daily to your Mailbox; hard ones only

It is currently 15 Dec 2018, 15:00

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 in December
PrevNext
SuMoTuWeThFrSa
2526272829301
2345678
9101112131415
16171819202122
23242526272829
303112345
Open Detailed Calendar
  • $450 Tuition Credit & Official CAT Packs FREE

     December 15, 2018

     December 15, 2018

     10:00 PM PST

     11:00 PM PST

    Get the complete Official GMAT Exam Pack collection worth $100 with the 3 Month Pack ($299)
  • FREE Quant Workshop by e-GMAT!

     December 16, 2018

     December 16, 2018

     07:00 AM PST

     09:00 AM PST

    Get personalized insights on how to achieve your Target Quant Score.

At a certain restaurant, the average (arithmetic mean) number of custo

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

Hide Tags

Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51218
At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 21 Aug 2015, 04:15
1
3
00:00
A
B
C
D
E

Difficulty:

  5% (low)

Question Stats:

86% (01:20) correct 14% (02:02) wrong based on 128 sessions

HideShow timer Statistics

At a certain restaurant, the average (arithmetic mean) number of customers served for the past x days was 75. If the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x?

A. 2
B. 5
C. 9
D. 15
E. 30

Kudos for a correct solution.

_________________

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

CEO
CEO
avatar
S
Joined: 20 Mar 2014
Posts: 2633
Concentration: Finance, Strategy
Schools: Kellogg '18 (M)
GMAT 1: 750 Q49 V44
GPA: 3.7
WE: Engineering (Aerospace and Defense)
GMAT ToolKit User Premium Member Reviews Badge
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 21 Aug 2015, 04:20
1
Bunuel wrote:
At a certain restaurant, the average (arithmetic mean) number of customers served for the past x days was 75. If the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x?

A. 2
B. 5
C. 9
D. 15
E. 30

Kudos for a correct solution.


Per the question,

\(\frac{75x+120}{x+1}\) =90 ---> x =2. A is the correct answer.
Director
Director
avatar
P
Joined: 21 May 2013
Posts: 652
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 21 Aug 2015, 05:14
1
Bunuel wrote:
At a certain restaurant, the average (arithmetic mean) number of customers served for the past x days was 75. If the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x?

A. 2
B. 5
C. 9
D. 15
E. 30

Kudos for a correct solution.



No of customers/No of days=75
C/x=75
C=75x
Now, C+120/x+1=90
Put C=75x from the earlier equation,
15x=30
x=2
Answer A
Senior Manager
Senior Manager
User avatar
S
Joined: 21 Jan 2015
Posts: 357
Location: India
Concentration: Strategy, Marketing
GMAT 1: 620 Q48 V28
GMAT 2: 690 Q49 V35
WE: Sales (Consumer Products)
GMAT ToolKit User CAT Tests
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 21 Aug 2015, 20:13
Bunuel wrote:
At a certain restaurant, the average (arithmetic mean) number of customers served for the past x days was 75. If the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x?

A. 2
B. 5
C. 9
D. 15
E. 30


Ans: A
Solution: from the given info we can say if N is the total number of people served in x says then avg 75=N/x = N=75x
and after todayavg 90= (N+120)/(x+1); puttine the value of N we get the x=2
_________________

--------------------------------------------------------------------
The Mind is Everything, What we Think we Become.

Director
Director
User avatar
G
Joined: 23 Jan 2013
Posts: 568
Schools: Cambridge'16
At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 21 Aug 2015, 22:11
1
Algebraic:

y/x=75
(y+120)/(x+1)=90
75x+120=90x+90
30=15x => x=2

Backsolving:

take 9 (C) 75*9=675+120=795/10=79.5, too low average so should take less days
take 5 (B) 75*5=375+120=495/6=82.5, low again but going up, so must be 2

A
Manager
Manager
avatar
Joined: 09 Jan 2013
Posts: 75
Concentration: Entrepreneurship, Sustainability
GMAT 1: 650 Q45 V34
GMAT 2: 740 Q51 V39
GRE 1: Q790 V650
GPA: 3.76
WE: Other (Pharmaceuticals and Biotech)
Reviews Badge
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 22 Aug 2015, 00:09
1
Equating total number of customers served
75x+120 = 90(x+1)
=> 15x = 30
x=2

Answer A.
Manager
Manager
avatar
B
Joined: 06 Jan 2014
Posts: 60
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 23 Aug 2015, 02:20
1
Total Customers Served in X days = 75x

Total customers served after today 75x+120

New Average (75x+120)/x+1 = 90

Solving X =2 ( Option A)
_________________

______________________________
Liked the Post !!!! KUDOs Plzzzzz

Manager
Manager
User avatar
Joined: 10 Jun 2015
Posts: 118
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 23 Aug 2015, 03:40
1
Bunuel wrote:
At a certain restaurant, the average (arithmetic mean) number of customers served for the past x days was 75. If the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x?

A. 2
B. 5
C. 9
D. 15
E. 30

Kudos for a correct solution.


the increase in average is 15
the increase in customers from the mean is 45
45/15 = 3 is x+1
Therefore, x=2
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 51218
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 23 Aug 2015, 11:22
1
1
Bunuel wrote:
At a certain restaurant, the average (arithmetic mean) number of customers served for the past x days was 75. If the restaurant serves 120 customers today, raising the average to 90 customers per day, what is the value of x?

A. 2
B. 5
C. 9
D. 15
E. 30

Kudos for a correct solution.


GROCKIT OFFICIAL SOLUTION:

WITHOUT using the formula, we can see that today the restaurant served 30 customers above the average. The total amount ABOVE the average must equal total amount BELOW the average. This additional 30 customers must offset the “deficit” below the average of 90 created on the x days the restaurant served only 75 customers per day.

30/15 = 2 days. Choice (A).

WITH the formula, we can set up the following:

90 = (75x + 120)/(x + 1)

90x + 90 = 75x + 120

15x = 30

x = 2 Answer Choice (A)

Use whichever makes more sense to you!
_________________

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

Intern
Intern
avatar
Joined: 30 Sep 2013
Posts: 20
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 24 Aug 2015, 08:18
HI Bunnel,

If you could you explain more elaborately, that would be very helpful.
Senior Manager
Senior Manager
avatar
Joined: 15 Sep 2011
Posts: 326
Location: United States
WE: Corporate Finance (Manufacturing)
GMAT ToolKit User
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 24 Aug 2015, 17:20
riteshgmat wrote:
HI Bunnel,

If you could you explain more elaborately, that would be very helpful.



Hi riteshgmat

Perhaps I can be of assistance. He means, whatever the residual is, it must be spread across the days equally, one part below and another above. The residual here is 30 days (\(120 - 90 = 30\)) and so to have the new average be 90, it must have been split into two \(15\)s and therefore, the number of days is \(2\).

Kr,
Ron
Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2627
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User Premium Member
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 16 Dec 2016, 16:03
Non-Human User
User avatar
Joined: 09 Sep 2013
Posts: 9166
Premium Member
Re: At a certain restaurant, the average (arithmetic mean) number of custo  [#permalink]

Show Tags

New post 05 Oct 2018, 04:06
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

GMAT Club Bot
Re: At a certain restaurant, the average (arithmetic mean) number of custo &nbs [#permalink] 05 Oct 2018, 04:06
Display posts from previous: Sort by

At a certain restaurant, the average (arithmetic mean) number of custo

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


Copyright

GMAT Club MBA Forum Home| About| Terms and Conditions and Privacy Policy| 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®.