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

It is currently 30 Aug 2014, 08:57

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

Joe bought only twenty cent stamps and thirty cent stamps.

  Question banks Downloads My Bookmarks Reviews Important topics  
Author Message
TAGS:
1 KUDOS received
Manager
Manager
avatar
Joined: 04 Apr 2010
Posts: 73
Schools: UCLA Anderson
Followers: 1

Kudos [?]: 13 [1] , given: 6

Joe bought only twenty cent stamps and thirty cent stamps. [#permalink] New post 16 Jun 2010, 12:01
1
This post received
KUDOS
00:00
A
B
C
D
E

Difficulty:

(N/A)

Question Stats:

33% (02:47) correct 67% (00:47) wrong based on 3 sessions
Joe bought only twenty cent stamps and thirty cent stamps. How many twenty cent stamps did he buy?

(1) Joe bought more than 8 twenty cent stamps.
(2) Joe bought a total of $2.50 worth of stamps.

Just want to make sure my reasoning is correct on this one - we can only use integers values for the numbers stamps, correct?
[Reveal] Spoiler: OA
2 KUDOS received
Ms. Big Fat Panda
Ms. Big Fat Panda
User avatar
Status: Biting Nails Into Oblivion
Joined: 09 Jun 2010
Posts: 1855
Followers: 337

Kudos [?]: 1373 [2] , given: 194

GMAT ToolKit User GMAT Tests User
Re: Another stamp question... twenty & thirty cent stamps [#permalink] New post 16 Jun 2010, 12:50
2
This post received
KUDOS
I am not sure if this is the most accurate solution, but here's my explanation as to why the answer is C.

Looking at the first statement:

20 cent stamps: > 8

This is insufficient, so we can eliminate answer choices A and D

Now looking at second statement, we see that 0.20a + 0.30 b = 2.5

But there are many possible values that will satisfy this condition, and hence this statement is insufficient by itself. So we can eliminate B.

Combining the two statements, we know that a > 8, so let us assume a = x + 8 where x can take the values of 1, 2, 3 and so on (Number of stamps can only be integers; you can't buy half a stamp :D)

Substituting a = x+8 into the equation we had from statement 2 we get

0.20a + 0.30b = 2.5

0.20(x+8) + 0.30b = 2.5

0.20x + 1.60 + 0.30b = 2.5

0.20x + 0.30b = 2.5 - 1.6 = 0.9

Now, we know that x can take the values of 1, 2 and 3 and so on

For x = 1 b = \frac {0.7}{0.3} - Eliminate (Not an integer)

For x = 2 b = \frac {0.5}{0.3} - Eliminate (Not an integer)

For x = 3 b = 1 - This is an integer, that would give rise to the answer being a = 11 and b = 1. But to be sure, we can check one or two more values.

For x = 4, b = \frac{0.1}{0.3}

For x = 5, b becomes negative. So we can stop here.

Hence, on combining the statements we see it's sufficient to answer the question.

Hope this helps. I wonder if there are other shorter methods to figure this out?
Manager
Manager
User avatar
Joined: 15 Apr 2010
Posts: 196
Followers: 3

Kudos [?]: 14 [0], given: 29

GMAT Tests User
Re: Another stamp question... twenty & thirty cent stamps [#permalink] New post 16 Jun 2010, 13:05
thanks for the answer above.... my solution is similar but doesnt use equations....

I assumed 9 *20cents stamps => 1.80 => 70 cents leftover (but this is not a integer value for the # of 30 cent stamps!)

so i moved to 10*20 cent stamps => 2.00 with 50 cents leftover for calculating # of 30 cent stamps used and yet again, we see that we dont get integer value for the # of 30 cent stamps....ie: 50/30=> 1.67 30c stamps....

hence the answer is 11 20cent stamps yielding 1 30cent stamp ...11,1 is the pair and good answer

hence C.
Manager
Manager
avatar
Joined: 04 Apr 2010
Posts: 73
Schools: UCLA Anderson
Followers: 1

Kudos [?]: 13 [0], given: 6

Re: Another stamp question... twenty & thirty cent stamps [#permalink] New post 16 Jun 2010, 14:27
Thanks guys! Good reasoning for both responses. Pran's solution is a little faster but both work.
Re: Another stamp question... twenty & thirty cent stamps   [#permalink] 16 Jun 2010, 14:27
    Similar topics Author Replies Last post
Similar
Topics:
5 Experts publish their posts in the topic Joe bought only twenty cent stamps and thirty cent stamps. rite2deepti 7 13 Dec 2010, 05:53
Joe bought only $0.20 stamps and $0.30 stamps. How many TheGmatTutor 1 15 Jun 2010, 16:29
Joanna bought only $0.15 stamps and $0.29 stamps apollo168 7 19 Aug 2006, 00:15
The price of postage stamps has increased 5 cents per year sudhagar 11 30 Oct 2005, 00:31
Joanna bought only $0.15 stamps and $0.29 stamps mba4me 4 10 Sep 2004, 09:09
Display posts from previous: Sort by

Joe bought only twenty cent stamps and thirty cent 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®.