confirm pls?

magical cook · Posted: Thu Jan 03, 2008 2:16 pm Post subject: confirm pls?

If x and y are positive integers and y = √(9 - x) , what is the value of y?
(1) x <8> 1

my answer and OA is different - I want to confirm the answer.

camitava · Posted: Thu Jan 03, 2008 2:26 pm Post subject:

Hey Magical cook, if I am not wrong, u have not posted the query correctly. Option - 2 is missing, I think!

magical cook · Posted: Thu Jan 03, 2008 3:14 pm Post subject:

sorry for some reason form got broken.

Can you take a look?

camitava · Posted: Thu Jan 03, 2008 3:17 pm Post subject:

Hey Magical cook, IMO E. By the way, what's the OA?

StarDust845 · Posted: Thu Jan 03, 2008 5:33 pm Post subject:

Is the answer D?

I am assuming sqrt(4) is +2. We consider only the principal square roots of numbers right?

Calista.

magical cook · Posted: Thu Jan 03, 2008 7:00 pm Post subject:

I think E but OA says C....

camitava · Posted: Thu Jan 03, 2008 7:33 pm Post subject:

The Qs is saying - X and Y are positive integers and y = sqrt(9 - x). If so and if we go with the OA as C, we can check the values of X and Y.

If X = 1, Y = sqrt( Cool

---> Y is not coming as integer
If X = 2, Y = sqrt(7) ---> Y is not coming as integer
If X = 3, Y = sqrt(6) ---> Y is not coming as integer
If X = 4, Y = sqrt(5) ---> Y is not coming as integer
If X = 5, Y = sqrt(4) ---> Y is coming as integer
If X = 6, Y = sqrt(3) ---> Y is not coming as integer
If X = 7, Y = sqrt(2) ---> Y is not coming as integer

So here we go. We can get the unique value of X and Y. So the OA is fine and we took a wrong approach to solve it. So now IMO C. A great miss in our approach - u can say Magical Cook! Crying or Very sad

StarDust845 · Posted: Thu Jan 03, 2008 8:17 pm Post subject:

What are you talking bt?

Given:
a) x and y are positive integers
b) y = sqrt(9-x)

Stmt 1) x < 8
implies x =1,2,...7 now only for x = 5 does y have an integer value. And in GMAT we take sqrt(4) as positive 2. So y = 2. Hence A or D

Note: You can't say "well, we don't know what x is", x MUST have a value so that y is a positive integer. And the only way that can happen is if x = 5 and then y = 2.

Stmt 2) y > 1
implies y = 2,3,4,... but y can't be 3,4,5,6,... because then x must be 0 or negative respectively. But given x is not 0 and not negative. So the only way x can be positive integer is when y = 2.

Hence answer is D. The OA must be wrong.

(I see only one problem.. if the sqrt(4) can be considered +2 or -2 then the answer is C, but sqrt(n) where n is a positive integer is always +ve for GMAT. There is also a thread on that earlier...hmm.. here it is http://www.beatthegmat.com/can-we-consider-sqrt-n-be-negative-t7618.html).

Calista.

camitava · Posted: Thu Jan 03, 2008 8:22 pm Post subject:

StarDust845, sorry sir, my mistake! Ufff, ur first statement - "What r u talking abt" - just put me on the ground otherwise I was flying high!!! Wink

StarDust845 · Posted: Thu Jan 03, 2008 8:27 pm Post subject:

I apologize. I didn't mean to be disrespectful or anything. I didn't understand what you were saying at all. So I wanted to give a thorough piece by piece approach of how I came to the conclusion (By the way it is maam not sir Smile

)

Calista.

jaiswaln · Posted: Fri Jan 04, 2008 7:03 am Post subject:

Y and X can't be negative hence the possibility of 4^0.5 being -2 is ruled out.

so the answer is D...

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FUNNY THOUGH.