Find all School-related info fast with the new School-Specific MBA Forum

It is currently 21 Oct 2014, 17:47

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.

Events & Promotions

Events & Promotions in June
Open Detailed Calendar

Joanna bought only $0.15 stamps and $0.29 stamps

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
Senior Manager
Senior Manager
avatar
Joined: 14 Jul 2006
Posts: 281
Followers: 1

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

Joanna bought only $0.15 stamps and $0.29 stamps [#permalink] New post 19 Aug 2006, 00:15
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

0% (00:00) correct 0% (00:00) wrong based on 0 sessions
Hi guys is there a better way to attack these types of question outside of trial and error?

Joanna bought only $0.15 stamps and $0.29 stamps. How many $0.15 stamps did she buy?
1) She bought $4.40 worth of stamps.
2) She bought an equal number of $0.15 stamps and $0.29 stamps.

In this case i assumed that the only way to satisfy condition one is if the 29 cent stamp would be either 5 or 10 so as to open the possibility that 440-29x is divisible by 15. Is this a valid assumption?

But what if the question were to be something like this

Martha bought several pencils. If each pencil was either a 23 cent pencil or a 21 cent pencil, how many 23 cent pencil did Martha buy?

1) Martha bought a total of 6 pencils
2) The total value of the pencils bought was 130
CEO
CEO
User avatar
Joined: 20 Nov 2005
Posts: 2922
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
Followers: 15

Kudos [?]: 81 [0], given: 0

 [#permalink] New post 19 Aug 2006, 00:58
Q1: A
Here is my approach:

Total = 15x+29y

St1: 15x+29y = 440
this means 29y must be a multiple of 5. So y could be 5 or 10
If y = 10 then x = 10
if y = 5 then x = 295/15 which is not an integer.
So x = 10 and y = 10 : SUFF

St2: x = y: INSUFF


Q2: B

St1: x +y = 6: INSUFF

St2: 21x+23y = 135
y could vary from 1 to 5
When y =
1. 5 then x = 0 :yes
2. 4 then x = 43/21 :no
3. 3 then x = 66/21 :no
4. 2 then x = 89/21 :no
5. 1 then x = 112/21 :no
SUFF
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

Senior Manager
Senior Manager
avatar
Joined: 14 Jul 2006
Posts: 281
Followers: 1

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

 [#permalink] New post 19 Aug 2006, 01:03
Thanks :) So in question 2 you really have to plug in values.
Manager
Manager
avatar
Joined: 09 Jul 2006
Posts: 85
Location: India
Followers: 1

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

 [#permalink] New post 19 Aug 2006, 11:46
ps_dahiya wrote:
Q1: A
Here is my approach:

Total = 15x+29y

St1: 15x+29y = 440
this means 29y must be a multiple of 5. So y could be 5 or 10
If y = 10 then x = 10
if y = 5 then x = 295/15 which is not an integer.
So x = 10 and y = 10 : SUFF

St2: x = y: INSUFF


Q2: B

St1: x +y = 6: INSUFF

St2: 21x+23y = 135
y could vary from 1 to 5
When y =
1. 5 then x = 0 :yes 21x + 115 = 135; x=20/21. Thus answer should be E
2. 4 then x = 43/21 :no
3. 3 then x = 66/21 :no
4. 2 then x = 89/21 :no
5. 1 then x = 112/21 :no
SUFF


My approach to the first problem was
from 1, 15x + 29y = 440
from 2, x = y
combining both, we have 44x=440;x=10 and y=10.
Hence (C).
Could you please explain what is wrong with this logic pls? Also is (E) the correct answer for problem 2 ? (my stmt in red in the quote above)
_________________

Cheers!
Prashrash.

GMAT Instructor
avatar
Joined: 04 Jul 2006
Posts: 1269
Location: Madrid
Followers: 23

Kudos [?]: 132 [0], given: 0

 [#permalink] New post 19 Aug 2006, 13:03
ps_dahiya wrote:
Q1: A
Here is my approach:

Total = 15x+29y

St1: 15x+29y = 440
this means 29y must be a multiple of 5. So y could be 5 or 10
If y = 10 then x = 10
if y = 5 then x = 295/15 which is not an integer.
So x = 10 and y = 10 : SUFF

St2: x = y: INSUFF


Q2: B

St1: x +y = 6: INSUFF

St2: 21x+23y = 135
y could vary from 1 to 5
When y =
1. 5 then x = 0 :yes
2. 4 then x = 43/21 :no
3. 3 then x = 66/21 :no
4. 2 then x = 89/21 :no
5. 1 then x = 112/21 :no
SUFF


Careful, ps_dahiya, you have been gifted with a fine math mind, but the last part needs to be reworked due to a careless error!

Obviously 130 is not a multiple of either 21 or 23, and 130=21(6)+4


i.e. 6 21cent pencils only would fall 4cents short of 1.30, so 'trade' two of them for 23cent pencils. No other comination will total $1.30
CEO
CEO
User avatar
Joined: 20 Nov 2005
Posts: 2922
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
Followers: 15

Kudos [?]: 81 [0], given: 0

 [#permalink] New post 19 Aug 2006, 20:48
kevincan wrote:
ps_dahiya wrote:
Q1: A
Here is my approach:

Total = 15x+29y

St1: 15x+29y = 440
this means 29y must be a multiple of 5. So y could be 5 or 10
If y = 10 then x = 10
if y = 5 then x = 295/15 which is not an integer.
So x = 10 and y = 10 : SUFF

St2: x = y: INSUFF


Q2: B

St1: x +y = 6: INSUFF

St2: 21x+23y = 135
y could vary from 1 to 5
When y =
1. 5 then x = 0 :yes
2. 4 then x = 43/21 :no
3. 3 then x = 66/21 :no
4. 2 then x = 89/21 :no
5. 1 then x = 112/21 :no
SUFF


Careful, ps_dahiya, you have been gifted with a fine math mind, but the last part needs to be reworked due to a careless error!

Obviously 130 is not a multiple of either 21 or 23, and 130=21(6)+4


i.e. 6 21cent pencils only would fall 4cents short of 1.30, so 'trade' two of them for 23cent pencils. No other comination will total $1.30

Thanks Kevin. These silly mistakes are a big problem for me. Could you please suggest, how can I avoid these? Should I read the question twice or should I read the solution twice or something else????
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

GMAT Instructor
avatar
Joined: 04 Jul 2006
Posts: 1269
Location: Madrid
Followers: 23

Kudos [?]: 132 [0], given: 0

 [#permalink] New post 20 Aug 2006, 00:29
IF you are very fast, then do what I did in the school, do each question twice. People rarely make the same silly mistake twice
CEO
CEO
User avatar
Joined: 20 Nov 2005
Posts: 2922
Schools: Completed at SAID BUSINESS SCHOOL, OXFORD - Class of 2008
Followers: 15

Kudos [?]: 81 [0], given: 0

 [#permalink] New post 20 Aug 2006, 00:35
kevincan wrote:
IF you are very fast, then do what I did in the school, do each question twice. People rarely make the same silly mistake twice

I got what you are saying but I am not very fast. Just to give you an idea, I generally complete the quant section 5-10 minutes early with a minimum score of 49. So it is not feasible to complete each question twice. Any other suggestions????
_________________

SAID BUSINESS SCHOOL, OXFORD - MBA CLASS OF 2008

  [#permalink] 20 Aug 2006, 00:35
    Similar topics Author Replies Last post
Similar
Topics:
43 Experts publish their posts in the topic Joanna bought only $0.15 stamps and $0.29 stamps. How many udaymathapati 27 26 Sep 2010, 10:48
Joanna bought only $0.15 stamps and $0.29 stamps. How many sam76 2 24 Feb 2008, 17:15
Joanna bought only $0.15 stamps and $0.29 stamps. How many gluon 9 15 Sep 2007, 14:45
Q30: Joanna bought only $0.15 stamps and $0.29 stamps. How nakib77 5 13 Oct 2005, 13:02
Joanna bought only $0.15 stamps and $0.29 stamps. How many DLMD 17 05 Feb 2005, 20:14
Display posts from previous: Sort by

Joanna bought only $0.15 stamps and $0.29 stamps

  Question banks Downloads My Bookmarks Reviews Important topics  


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

Powered by phpBB © phpBB Group and phpBB SEO

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®.