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Simple algebra ques .but not matching answer given at end

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Simple algebra ques .but not matching answer given at end

by pardeep_10sharma » Sun May 16, 2010 12:51 am
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.

The ans given at end is A but i am getting C. Plz confirm..........
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by Gmat_War » Sun May 16, 2010 6:14 am
Let us assume that he bought x $0.15 stamps and y $0.29 stamps.
From statement 1 we get
0.15x +0.29y=4.40
=> 0.15x =4.40-0.29y
=> 15x=440-29y
This implies that the right side pf the equation should be a multiple of 15 since x should be an integer.
So y can have values 5,10,15(IT cannot be 0 since number of $0.29 coins cannot be 0)
However y cannot be 15 since then the equation becomes
15x=440 -435=5 and hence this is not divisible by 15.
Also y cannot be 5 since then the equation becomes
15x=440 -145=295 which is not divisible by 15.
So y has to be 10.
Only if y=10,x=(440-290)/15=10 and thus we can uniquely determine the number of $0.15 coins.Hence A
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by pardeep_10sharma » Mon May 17, 2010 4:51 am
what a style to solve ques man.Awesome..........Thanks 4 sharing this view. This is really good. Keep on solving my ques man.there are a lot more to come...............Many many thanks
Gmat_War wrote:Let us assume that he bought x $0.15 stamps and y $0.29 stamps.
From statement 1 we get
0.15x +0.29y=4.40
=> 0.15x =4.40-0.29y
=> 15x=440-29y
This implies that the right side pf the equation should be a multiple of 15 since x should be an integer.
So y can have values 5,10,15(IT cannot be 0 since number of $0.29 coins cannot be 0)
However y cannot be 15 since then the equation becomes
15x=440 -435=5 and hence this is not divisible by 15.
Also y cannot be 5 since then the equation becomes
15x=440 -145=295 which is not divisible by 15.
So y has to be 10.
Only if y=10,x=(440-290)/15=10 and thus we can uniquely determine the number of $0.15 coins.Hence A
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