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

It is currently 15 Oct 2018, 10:51

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

If john makes a contribution to a charity fund at school, th

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

Hide Tags

Intern
Intern
avatar
Joined: 15 Jan 2010
Posts: 6
If john makes a contribution to a charity fund at school, th  [#permalink]

Show Tags

New post 22 Jan 2010, 11:16
22
00:00
A
B
C
D
E

Difficulty:

  55% (hard)

Question Stats:

68% (01:53) correct 32% (02:12) wrong based on 638 sessions

HideShow timer Statistics

If john makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person. If there were 5 other contributions made before john's, what is the size of his donation?

A. $100
B. $150
C. $200
D. $250
E. $450
Most Helpful Expert Reply
Math Expert
User avatar
V
Joined: 02 Sep 2009
Posts: 49858
Re: 700-800 level problem Statistics  [#permalink]

Show Tags

New post 22 Jan 2010, 11:35
3
5
GMAT10 wrote:
If john makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person.If there were 5 other contributions made before john's,what is the size of his donation?
a)$100
b)$150
c)$200
d)$250
e)$450

Please solve?


Let \(a\) be the average contribution size before John makes his contribution.
Let \(c\) be the total contribution size before John makes his contribution.
Let \(x\) be John's contribution.

\(1.5a=75\) --> \(a=50\)

\(a=50=\frac{c}{5}\) --> \(c=250\)

\(\frac{c+x}{6}=75\) --> \(\frac{250+x}{6}=75\) --> \(x=200\)

Answer: C.
_________________

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

Most Helpful Community Reply
CEO
CEO
User avatar
Status: Nothing comes easy: neither do I want.
Joined: 12 Oct 2009
Posts: 2608
Location: Malaysia
Concentration: Technology, Entrepreneurship
Schools: ISB '15 (M)
GMAT 1: 670 Q49 V31
GMAT 2: 710 Q50 V35
Reviews Badge
Re: 700-800 level problem Statistics  [#permalink]

Show Tags

New post 22 Jan 2010, 11:33
7
2
yes 200 is the ans.

final avg = 75 = 1.5 of old

i.e old avg = 50 = total of five/5

total of five = 250

new avg = 75 = total of six/6

total of 6 = 450

so John's contribution = 450-250 =200
_________________

Fight for your dreams :For all those who fear from Verbal- lets give it a fight

Money Saved is the Money Earned :)

Jo Bole So Nihaal , Sat Shri Akaal

:thanks Support GMAT Club by putting a GMAT Club badge on your blog/Facebook :thanks

GMAT Club Premium Membership - big benefits and savings

Gmat test review :
http://gmatclub.com/forum/670-to-710-a-long-journey-without-destination-still-happy-141642.html

General Discussion
Intern
Intern
User avatar
Joined: 21 Jan 2010
Posts: 48
Location: Canada
Re: 700-800 level problem Statistics  [#permalink]

Show Tags

New post 22 Jan 2010, 11:20
3
1
Cavg = average contribution before John

Cavg*1.5 = 75, therefore the average cont is $50 before John.

If he needs to increase the average contribution by $25, he must put in $25 for each of the 5 people.
so $125.
But, he also has to put in the average for himself (the sixth person), so add $75.

So $200 is your answer.
_________________

________________________________________________________________________
Andrew
http://www.RenoRaters.com

Manager
Manager
avatar
Joined: 07 Aug 2011
Posts: 51
Concentration: Entrepreneurship, Finance
GPA: 3.87
Re: Contribution to a charity Fund  [#permalink]

Show Tags

New post 17 Nov 2011, 17:25
If, after John's donation, the average was $75 per person then the total is $75(6) which comes to a total of 450 contributed dollars by all donees. If John's donation increases the total contributions by 50% then it is now 150% of what it was and John's contribution was 1/3 of that, which would be 1/3 of the $450. John contributed $150.

Answer B.
Manager
Manager
avatar
Status: D-Day is on February 10th. and I am not stressed
Affiliations: American Management association, American Association of financial accountants
Joined: 12 Apr 2011
Posts: 180
Location: Kuwait
Schools: Columbia university
Re: Contribution to a charity Fund  [#permalink]

Show Tags

New post Updated on: 18 Nov 2011, 14:48
ok here is how I approached this question:

I, first, got the original average before the increase and without john's:

1.5x=75
x=50

then, I got the sum of the contributions of the 5 dominees without John:

5x/5=50
hence, 5x=250

after that, i set up the average equation with john's contribution:

250+x/6=75

250+x=75(6)

250+x=450
hence, x, which is John's amouts= 200
so the answer I got is C, hope this helps
_________________

Sky is the limit


Originally posted by manalq8 on 18 Nov 2011, 02:43.
Last edited by manalq8 on 18 Nov 2011, 14:48, edited 1 time in total.
Manager
Manager
avatar
Joined: 07 Aug 2011
Posts: 51
Concentration: Entrepreneurship, Finance
GPA: 3.87
Re: Contribution to a charity Fund  [#permalink]

Show Tags

New post 18 Nov 2011, 08:52
1
Thought I'd write my reasoning out in a more quantitative form.

J = {6($75)}/3, or J = [{1($75) +5($75)}/150]*50. The key, I think, is to realize that John's contribution was 1/3 of all the current contributions. Since we know the total contribution is 6($75)=$450, then we know his contribution was 1/3 of that. 1/3*450=$150.
Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8373
Location: Pune, India
Re: Contribution to a charity Fund  [#permalink]

Show Tags

New post 20 Nov 2011, 01:07
1
enigma123 wrote:
If John makes a contribution to a charity fund at school, the average contribution size will increase by 50%, reaching $75 per person. If there were 5 other contributions made before John’s, what is the size of his donation?
(A) $100
(B) $150
(C) $200
(D) $250
(E) $450

OA is not provided, but I have got C. Do you guys think C is the right answer?


Responding to a pm:

After John's contribution, the average size increases by 50% and reaches $75. What must have been the average size of contribution before John's donation? It must have been $50 since a 50% increase would lead us to $75.
$50 was the average size for 5 donations. Total amount donated = $250
$75 is the average size for 6 donations. Total amount donated = $450
John's contribution must have been 450 - 250 = $200

Answer (C)
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

Veritas Prep GMAT Instructor
User avatar
P
Joined: 16 Oct 2010
Posts: 8373
Location: Pune, India
Re: Contribution to a charity Fund  [#permalink]

Show Tags

New post 20 Nov 2011, 09:04
1
Stoneface wrote:
If, after John's donation, the average was $75 per person then the total is $75(6) which comes to a total of 450 contributed dollars by all donees. If John's donation increases the total contributions by 50% then it is now 150% of what it was and John's contribution was 1/3 of that, which would be 1/3 of the $450. John contributed $150.

Answer B.


Responding to a pm:

We cannot say that John's contribution is a third. To increase the average by 50%, you need to invest more than a third of the total. The reason is that previous average is for 5 people. New average has another person so the total contribution needs to be higher.

The total contribution now = 75*6 = 450
Out of this, if 150 were contributed by John, the previous total contribution must have been 300. With 5 people, that would mean an average of 60. We need 6 people to make the average 50 but before John made the contribution, there were only 5 people. That's where you made a mistake. Since a person increases, the contribution needs to be even higher than a third.
_________________

Karishma
Veritas Prep GMAT Instructor

Learn more about how Veritas Prep can help you achieve a great GMAT score by checking out their GMAT Prep Options >

GMAT self-study has never been more personalized or more fun. Try ORION Free!

Manager
Manager
avatar
Joined: 07 Aug 2011
Posts: 51
Concentration: Entrepreneurship, Finance
GPA: 3.87
Re: Contribution to a charity Fund  [#permalink]

Show Tags

New post 21 Nov 2011, 07:02
I do not understand at all, but thanks for your time. I think I'll spend a little extra time in the ol' GMAT book today.
Intern
Intern
User avatar
Joined: 27 Feb 2015
Posts: 48
Concentration: General Management, Economics
GMAT 1: 630 Q42 V34
WE: Engineering (Transportation)
GMAT ToolKit User Reviews Badge
Re: If john makes a contribution to a charity fund at school, th  [#permalink]

Show Tags

New post 18 Oct 2016, 05:00
VeritasPrepKarishma wrote:
enigma123 wrote:
If John makes a contribution to a charity fund at school, the average contribution size will increase by 50%, reaching $75 per person. If there were 5 other contributions made before John’s, what is the size of his donation?
(A) $100
(B) $150
(C) $200
(D) $250
(E) $450

OA is not provided, but I have got C. Do you guys think C is the right answer?


Responding to a pm:

After John's contribution, the average size increases by 50% and reaches $75. What must have been the average size of contribution before John's donation? It must have been $50 since a 50% increase would lead us to $75.
$50 was the average size for 5 donations. Total amount donated = $250
$75 is the average size for 6 donations. Total amount donated = $450
John's contribution must have been 450 - 250 = $200

Answer (C)


I got this wrong by attempting this problem logically (Fan of your logical approach :) ), please let me know what's wrong in my logic.

New avg - 75 per person
old avg- 50 per person
so 25 per person was extra added by john , that mean John had Extra $
Extra John carried was = 25*(5+1) i.e. for 5 others and John
Extra = 150, this is the extra amount.
..oh no! I think while writing this I got my mistake (silly one!) . I'll still continue so that people who find this interesting will adopt this and not make silly error as me

So john contributed 150$ extra plus he also had the old avg amt. i.e. 50 $
so total john contributed is 150+50 = $200

You must have figured what mistake I did. I picked B.150$ . But that's just the extra amount John has apart from 50$.
Thanks.
Current Student
User avatar
D
Joined: 12 Aug 2015
Posts: 2638
Schools: Boston U '20 (M)
GRE 1: Q169 V154
GMAT ToolKit User Premium Member
Re: If john makes a contribution to a charity fund at school, th  [#permalink]

Show Tags

New post 11 Dec 2016, 09:00
Here is my take on this one -->
Mean 1=>50
Mean 2=>75
Sum(1)=50*5=250
Sum(2)=75*6=450.
Hence,John's contribution => 450-250=200.

Alternatively =>
John donated => 50+25*6=> 50+150=200.

Great explanation by VeritasPrepKarishma :-D :lol:


Regards
Stone Cold

_________________


MBA Financing:- INDIAN PUBLIC BANKS vs PRODIGY FINANCE!

Getting into HOLLYWOOD with an MBA!

The MOST AFFORDABLE MBA programs!

STONECOLD's BRUTAL Mock Tests for GMAT-Quant(700+)

AVERAGE GRE Scores At The Top Business Schools!

CEO
CEO
User avatar
D
Joined: 12 Sep 2015
Posts: 2993
Location: Canada
Re: If john makes a contribution to a charity fund at school, th  [#permalink]

Show Tags

New post 23 Jul 2018, 07:49
Top Contributor
GMAT10 wrote:
If john makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person. If there were 5 other contributions made before john's, what is the size of his donation?

A. $100
B. $150
C. $200
D. $250
E. $450


Let J = the John's donation
Let a, b, c, d and e = the donations of the other 5 donors.

John makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person.
If the average contribution for all 6 donors = $75, we can write: (a + b + c + d + e + J)/6 = $75
Multiply both sides by 6 to get: a + b + c + d + e + J = $450

John makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person.
If we let x = the OLD (before John) average donation, then we can write 1.5x = $75
Solve for x to get x = $50
So, $50 is the OLD (before John) average donation for donors a, b, c, d and e
We can write: (a + b + c + d + e)/5 = $50
Multiply both sides by 5 to get: a + b + c + d + e = $250

We now have two equations:
a + b + c + d + e + J = $450
a + b + c + d + e = $250

Subtract the bottom equation from the top equation to get: J = $200

Answer: C

RELATED VIDEO FROM OUR COURSE

_________________

Brent Hanneson – GMATPrepNow.com
Image
Sign up for our free Question of the Day emails

Target Test Prep Representative
User avatar
G
Status: Head GMAT Instructor
Affiliations: Target Test Prep
Joined: 04 Mar 2011
Posts: 2830
Re: If john makes a contribution to a charity fund at school, th  [#permalink]

Show Tags

New post 25 Jul 2018, 17:35
GMAT10 wrote:
If john makes a contribution to a charity fund at school, the average contribution size will increase by 50% reaching $75 per person. If there were 5 other contributions made before john's, what is the size of his donation?

A. $100
B. $150
C. $200
D. $250
E. $450



We can let the old average = a and create the equation:

1.5a = 75

a = 50

Thus, the original sum was 250.

So we can create another equation, where j = the size of John’s contribution:

75 = (j + 250)/6

450 = j + 250

200 = j

Answer: C
_________________

Jeffery Miller
Head of GMAT Instruction

GMAT Quant Self-Study Course
500+ lessons 3000+ practice problems 800+ HD solutions

GMAT Club Bot
Re: If john makes a contribution to a charity fund at school, th &nbs [#permalink] 25 Jul 2018, 17:35
Display posts from previous: Sort by

If john makes a contribution to a charity fund at school, th

  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®.