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m09 Q 18

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Intern
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Joined: 13 Jan 2010
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m09 Q 18 [#permalink] New post 07 Aug 2010, 15:27
Please can someone help solve this problem.

How much water (in grams) should be added to a 35%-solution of acid to obtain a 10%-solution?

There are 50 grams of the 35%-solution.
In the 35%-solution the ratio of acid to water is 7:13.

Statement (1) ALONE is sufficient, but Statement (2) ALONE is not sufficient
Statement (2) ALONE is sufficient, but Statement (1) ALONE is not sufficient
BOTH statements TOGETHER are sufficient, but NEITHER statement ALONE is sufficient
EACH statement ALONE is sufficient
Statements (1) and (2) TOGETHER are NOT sufficient
Manager
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Re: m09 Q 18 [#permalink] New post 08 Aug 2010, 10:40
I guess the answer is A. Only statement 1 is sufficient but not 2.

My approach is "AD/BCE"
In order to know the amount of water to be added we need to know the amount of acid present & the initial amount of solution.
Statement -1:: 50 grm solution & 35% acid = .35X50 = 17.5 gms acid. New solution will have 17.5 gms acid, which will make 10% of the total amount of the solution => total amount of solution = 175 gms => water to be added = 175 - 50 = 75 gms.
We can cancel 2nd part of AD/BCE i.e we are left with options A & D.
Statement 2-:: no new information is given. 35% acid solution => acid 35 gms & water 65 gms. Ratio 35/65 = 7:13. Tgis is not sufficient. Therefore option D is also wrong.
We are left with A. Which I think is the correct option.

please let me know what you think....
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Re: m09 Q 18 [#permalink] New post 08 Aug 2010, 11:34
Thanks for he explanation. I did not understand what you meant by "AD/BCE"?. Please can you elaborate to help me understand.
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Re: m09 Q 18 [#permalink] New post 08 Aug 2010, 13:05
For DS problem I always group the answer choices and work my way through by eliminating them till I get to the correct one.
I keep options A&D together and options BCE together and separate them by a "/" . it looks something like "AD / BCE". Then I go to the statements.
Now consider: (case I)
If statement 1 is sufficient
Then there are only two possibilities either only statement 1 is sufficient and 2 is not which gives you answer "A", or statement 2 is also sufficient that means both of them are sufficient which gives you answer choice "D". So keep them & cancel the other three option BCE. you are left with AD / [strike]BCE[/strike], you can straight way eliminate BCE. Consider the answer options, "B" = only 2, is wrong since 1 is already giving you the answer, "C" = combined, wrong, since 1 is already giving you the answer, "E" = not sufficient, since 1 is already giving you the answer.

Now that you are left with only 2 options A & D and the problem becomes bit simpler. You need only to check whether 2 is also sufficient. If 2 is then cancel out A & go for "D". Otherwise stick to A.
(case II)
If statement 1 is not sufficient
Then you can cancel out A&D and write [strike]AD[/strike] / BCE. now check for statement 2 and see whether it gives you an answer. If it does then B is the answer, if it does not then you have to check by combining. If that also fails then the answer is E.
I am just applying POE (process of elimination ) at the beginning to simplify my task and work with fewer answer choices.
Hope the explanation is clear. Its a bit lengthy :oops: but I could not manage to keep it more simple.
Re: m09 Q 18   [#permalink] 08 Aug 2010, 13:05
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