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

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Senior Manager
Joined: 28 Jun 2007
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Joanna bought only $0.15 stamps and$0.29 stamps. How many [#permalink]  15 Sep 2007, 14:45
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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.
VP
Joined: 09 Jul 2007
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Location: London
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Re: DS : Set 6, Q30 - Joanna and her stamps [#permalink]  15 Sep 2007, 15:00
gluon 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.

it is combined 1 and 2.

she bought equal number of stamps so it can be denoted by x
.15x+.29x=4.40
.44x=4.4
x=10

so she bought 10 of .15 and 10 of .29
Intern
Joined: 15 Sep 2007
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[#permalink]  15 Sep 2007, 18:38
Isn't (1) by itself sufficient to answer the question ? The only positive integer values of x and y that satifsy 0.15x+0.29y=4.40 are x=y=10.
Director
Joined: 09 Aug 2006
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[#permalink]  15 Sep 2007, 23:26
coldweather999 wrote:
Isn't (1) by itself sufficient to answer the question ? The only positive integer values of x and y that satifsy 0.15x+0.29y=4.40 are x=y=10.

Hey coolwaether999.. you are cool (right). Only 1 combination works that way.. So A is alone suff. How do you figure out these kind of solution ? I am sure, trial and error will consume lot of time ... do you just hear your ear on that ..?

But the OA that I have says the the correct ans as D. I am just not able to figure out how B alone suff..
can anyone shed some light..
CEO
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Re: DS : Set 6, Q30 - Joanna and her stamps [#permalink]  16 Sep 2007, 00:33
gluon 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.

S1)

$4.40--> 440 We know that 15(x) +29(y)=440. Since 440 has a 0 on the end of it we have to have 29(y) equal to a number that will give us 0 on the end. Since the other number is 15 we must multiply 29 by a number that will give us a 0 as the units digit. 29*10=290. 15*10=150 150+290=440. The only number that satisfys this condition for 29 is 10. Since 20*29 is too great. Suff. S2) This has to be insuff. Ok so the number is equal... so what... we aren't given any constraints as in S1. I really don't see how this can be suff since we can have an infinite number of values. Could have 5 stamps of .15 thus 5 stamps of .29. could have 15 stamps of .15 thus 15 of .29. These give us different values. Gluon wut do u have as the OA? Manager Status: Post MBA, working in the area of Development Finance Joined: 09 Oct 2006 Posts: 170 Location: Africa Followers: 1 Kudos [?]: 3 [0], given: 1 [#permalink] 16 Sep 2007, 01:15 Yes. D is the answer. Both the statements by themselves are sufficient. It took some time, but trial and error seemed to be the only way for me to arrive at making St. 1 suff. St. B is simple algebra. Amit05 wrote: coldweather999 wrote: Isn't (1) by itself sufficient to answer the question ? The only positive integer values of x and y that satifsy 0.15x+0.29y=4.40 are x=y=10. Hey coolwaether999.. you are cool (right). Only 1 combination works that way.. So A is alone suff. How do you figure out these kind of solution ? I am sure, trial and error will consume lot of time ... do you just hear your ear on that ..? But the OA that I have says the the correct ans as D. I am just not able to figure out how B alone suff.. can anyone shed some light.. VP Joined: 09 Jul 2007 Posts: 1108 Location: London Followers: 6 Kudos [?]: 74 [0], given: 0 Re: DS : Set 6, Q30 - Joanna and her stamps [#permalink] 16 Sep 2007, 02:45 gluon 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. how can 1 be alone sufficient. We cannot simply say she bought x numer of stamps of each how do we know that she bought equal number of stamps from 1 how can 2 be alone suffuicient. we do not know how much she spend. combined should be fine. Senior Manager Joined: 28 Jun 2007 Posts: 320 Followers: 1 Kudos [?]: 22 [0], given: 0 [#permalink] 16 Sep 2007, 06:22 The OA is A. I got it wrong while practising too and then the OA stunned me. I hate trick problems!! Ravshonbek... I agree with you that we should not assume that x = y for (1). But if you look closely we dont need to. This is a very tricky problem. We know that 0.15x + 0.29y = 4.40 If this was a generic equation then we could have x = -1 and y = (4.55/0.29) But, since Joanna is buying stamps it is implicit that x and y are positive integers. Joanna cannot buy -1 or (4.55/0.29) stamps. The only positive integers that satisfy this equation are x = 10, y = 10. Hence, (1) is sufficient. If there are some other positive integers that satisfy this equation then we would be correct about (1) being insufficient. Last edited by gluon on 16 Sep 2007, 06:40, edited 2 times in total. Manager Status: Post MBA, working in the area of Development Finance Joined: 09 Oct 2006 Posts: 170 Location: Africa Followers: 1 Kudos [?]: 3 [0], given: 1 [#permalink] 16 Sep 2007, 06:30 Speed kills! Careless error! St. by 2 itself is not suff. There could be innumerable combinations that could suffice the eqn. [Let the no. of stamps of$0.15 denomination be x and $0.29 deno. be y Then x*$0.15+y*$0.29=?] So, the trial and error will give the ans. A. Only the combination of 10 each of the two stamps suffice st.1 Remember the no. of stamps has to be +ve integer. Am not sure how B is suff.! Artemov wrote: Yes. D is the answer. Both the statements by themselves are sufficient. It took some time, but trial and error seemed to be the only way for me to arrive at making St. 1 suff. St. B is simple algebra. Amit05 wrote: coldweather999 wrote: Isn't (1) by itself sufficient to answer the question ? The only positive integer values of x and y that satifsy 0.15x+0.29y=4.40 are x=y=10. Hey coolwaether999.. you are cool (right). Only 1 combination works that way.. So A is alone suff. How do you figure out these kind of solution ? I am sure, trial and error will consume lot of time ... do you just hear your ear on that ..? But the OA that I have says the the correct ans as D. I am just not able to figure out how B alone suff.. can anyone shed some light.. Senior Manager Joined: 27 Aug 2007 Posts: 253 Followers: 1 Kudos [?]: 10 [0], given: 0 [#permalink] 16 Sep 2007, 07:10 I got into trap too, I have to read questions once again after finding the solution. Ans: A [#permalink] 16 Sep 2007, 07:10 Similar topics Replies Last post Similar Topics: 64 Joanna bought only$0.15 stamps and $0.29 stamps. How many 27 26 Sep 2010, 10:48 1 Joanna bought only$0.15 stamps and $0.29 stamps. How many 2 28 Jul 2010, 05:49 Joanna bought only$0.15 stamps and $0.29 stamps. How many 2 05 Jan 2010, 06:59 11 Joanna bought only$0.15 stamps and $0.29 stamps. How many 7 30 Nov 2009, 13:08 Joanna bought only$0.15 stamps and $0.29 stamps. How many 4 23 Sep 2008, 13:04 Display posts from previous: Sort by # Joanna bought only$0.15 stamps and \$0.29 stamps. How many

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