It is currently 14 Dec 2017, 07:22

# Decision(s) Day!:

CHAT Rooms | Wharton R1 | Stanford R1 | Tuck R1 | Ross R1 | Haas R1

### 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

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

# Events & Promotions

###### Events & Promotions in June
Open Detailed Calendar

# Joanna bought only $0.15 stamps and$0.29 stamps. How many

Author Message
Manager
Joined: 22 Jul 2008
Posts: 96

Kudos [?]: 243 [0], given: 11

Location: Bangalore,Karnataka
Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]

### Show Tags

05 Jan 2010, 06:59
00:00

Difficulty:

75% (hard)

Question Stats:

48% (01:07) correct 52% (01:18) wrong based on 33 sessions

### HideShow timer Statistics

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.

OPEN DISCUSSION OF THIS QUESTION IS HERE: http://gmatclub.com/forum/joanna-bought ... 01743.html
[Reveal] Spoiler: OA

Kudos [?]: 243 [0], given: 11

Math Expert
Joined: 02 Aug 2009
Posts: 5348

Kudos [?]: 6127 [0], given: 121

Re: Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]

### Show Tags

05 Jan 2010, 07:25
A...
si) gives us total to be 4.4... for it to be true .29 cost stamps have to be in multiple of 5 as .15 ,the other cost is a multiple of 5....
possiblity of 5 or 10 or15 stamps of .29 cost.... a) 4.4-.29*5 is not divisible by .15 so not true..
b) 4.4-.29*10 is divisible by .15 so possible .. c) 4.4-.29*15 is not divisible by .15 so not true..
thus we get 10 of each...suff
sii) is not suff
_________________

Absolute modulus :http://gmatclub.com/forum/absolute-modulus-a-better-understanding-210849.html#p1622372
Combination of similar and dissimilar things : http://gmatclub.com/forum/topic215915.html

Kudos [?]: 6127 [0], given: 121

Manager
Joined: 27 Aug 2009
Posts: 134

Kudos [?]: 34 [0], given: 1

Re: Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]

### Show Tags

05 Jan 2010, 10:17

Kudos [?]: 34 [0], given: 1

Manager
Joined: 09 Jun 2010
Posts: 71

Kudos [?]: 29 [0], given: 17

Re: Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]

### Show Tags

28 Jul 2010, 05:49
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 . I was thinking we need the total stamps as an addtional information so I picked E ! pleas help me understand thanks Kudos [?]: 29 [0], given: 17 Math Expert Joined: 02 Sep 2009 Posts: 42605 Kudos [?]: 135629 [1], given: 12705 Re: Joanna bought only$0.15 stamps and $0.29 stamps. How many [#permalink] ### Show Tags 28 Jul 2010, 05:59 1 This post received KUDOS Expert's post xmagedo wrote: 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 .

I was thinking we need the total stamps as an addtional information so I picked E !

pleas help me understand
thanks

Joanna bought only $0.15 stamps and$0.29 stamps. How many $0.15 stamps did she buy? Let $$x$$ be the # of$0.15 stamps and $$y$$ the # of $0.29 stamps. Note that $$x$$ and $$y$$ must be an integers. Q: $$x=?$$ (1) She bought$4.40 worth of stamps --> $$15x+29y=440$$. Only one integer combination of $$x$$ and $$y$$ is possible to satisfy $$15x+29y=440$$: $$x=10$$ and $$y=10$$. Sufficient.

(2) She bought an equal number of $0.15 stamps and$0.29 stamps --> $$x=y$$. Not sufficient.

So when we have equation of a type $$ax+by=c$$ and we know that $$x$$ and $$y$$ are non-negative integers, there can be multiple solutions possible for $$x$$ and $$y$$ (eg $$5x+6y=60$$) OR just one combination (eg $$15x+29y=440$$). Hence in some cases $$ax+by=c$$ is NOT sufficient and in some cases it is sufficient.

For more on this type of questions check: gmat-prep2-92785.html?hilit=stamps

Hope it helps.
_________________

Kudos [?]: 135629 [1], given: 12705

Intern
Joined: 03 Mar 2010
Posts: 40

Kudos [?]: 24 [0], given: 1

Re: Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]

### Show Tags

29 Jul 2010, 01:44
Statement 1: equation 15x+29y=440
since both 15x and 440 are multiples of 5 then y=5, 10, 15, 20, ...
since 290y<440 then y<20 then y=5, 10, 15
since 15x mod 3 = 0, 29 mod 3 = 2, 440 mod 3 = 2, then y mod 3 = 1, or y=10
sufficient

Statement 2: clearly not sufficient

Notation: (a mod b) gives remainder when divide a by b
_________________

Hardworkingly, you like my post, so kudos me.

Kudos [?]: 24 [0], given: 1

Math Expert
Joined: 02 Sep 2009
Posts: 42605

Kudos [?]: 135629 [0], given: 12705

Re: Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]

### Show Tags

14 Aug 2017, 00:55
Joanna bought only $0.15 stamps and$0.29 stamps. How many $0.15 stamps did she buy? Let $$x$$ be the # of$0.15 stamps and $$y$$ the # of $0.29 stamps. Note that $$x$$ and $$y$$ must be an integers. Q: $$x=?$$ (1) She bought$4.40 worth of stamps --> $$15x+29y=440$$. Only one integer combination of $$x$$ and $$y$$ is possible to satisfy $$15x+29y=440$$: $$x=10$$ and $$y=10$$. Sufficient.

(2) She bought an equal number of $0.15 stamps and$0.29 stamps --> $$x=y$$. Not sufficient.

OPEN DISCUSSION OF THIS QUESTION IS HERE: http://gmatclub.com/forum/joanna-bought ... 01743.html
_________________

Kudos [?]: 135629 [0], given: 12705

Re: Joanna bought only $0.15 stamps and$0.29 stamps. How many   [#permalink] 14 Aug 2017, 00:55
Display posts from previous: Sort by

# Joanna bought only $0.15 stamps and$0.29 stamps. How many

 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®.