1) If xy=1, what is the value of 2(x+Y)^2/ 2(x-Y)^2? a)2 b)4 : Quant Question Archive [LOCKED]
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# 1) If xy=1, what is the value of 2(x+Y)^2/ 2(x-Y)^2? a)2 b)4

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Manager
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1) If xy=1, what is the value of 2(x+Y)^2/ 2(x-Y)^2? a)2 b)4 [#permalink]

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01 May 2006, 11:08
This topic is locked. If you want to discuss this question please re-post it in the respective forum.

1) If xy=1, what is the value of 2(x+Y)^2/ 2(x-Y)^2?

a)2
b)4
c)8
d)16
e)32

2) If x is positive, is x>3?

a) (x-1)^2>4
b) (x-1)^2>9

The next one is really funny, I think is may be a misprint. But I'm not sure it GMAT Prep can have a misprint!!

3) n, m are positive intergers. What is the remainder when 3^(4n+2) is divided by 10?

a) n=2
b) m=1

Also guys, I notice my weak areas are inequalities and coordinate geometry. Can you please direct me to some good resources for these two areas. I have 5 days to go for the D-Day!
Manager
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01 May 2006, 12:18
I got the third one on the GMATPrep too. Must be a typo or wrong answer (the OA is "D", right?).

Frustrating. Hope the real GMAT doesn't have errors in it
VP
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01 May 2006, 14:33
How do u solve the first one?
Manager
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01 May 2006, 15:26
No way you can solve the 1st one i also got that question when i took the gmatprep it was q no 3 and obviously i had no clue what to do so just guessed something and obviously it was wrong ... i'm sure it would have changed my next question since i got that wrong .
Manager
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01 May 2006, 20:19
Phew! I was worried about these. Guys, what about the second question?
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01 May 2006, 21:25
2) If x is positive, is x>3?

a) (x-1)^2>4
b) (x-1)^2>9

St1:
(x-1)^2 - 4 > 0
(x-1+2)(x-1-2) > 0
(x+1)(x-3) > 0

x is valid for x < -1 or x > 3. Insufficient.

St2:
(x-1)^2 - 9 > 0
(x-1+3)(x-1-3) > 0
(x+2)(x-4) > 0

x is valid for x < -2 or x > 4. Insufficient.

Using St1 and St2:

x is valid for x < -1 or x > 3. Insufficient.

Ans E
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01 May 2006, 21:27
3) n, m are positive intergers. What is the remainder when 3^(4n+2) is divided by 10?

a) n=2
b) m=1

3^(4n+2)/10

St1: Even for us to sovle and find the remainder when divided by 10
St2: knowing m is useless as we do not have the variable m in the equation.

Ans A
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02 May 2006, 02:11
[quote="ywilfred"]2) If x is positive, is x>3?

a) (x-1)^2>4
b) (x-1)^2>9

St1:
(x-1)^2 - 4 > 0
(x-1+2)(x-1-2) > 0
(x+1)(x-3) >

Solving the first satement you get x<-1or x>3
The Question gives you the information that x is positive so x cant be less than -1 so x>3.
solving second equation x<-2 or x>4
but x cant be <-2 because x is positive so x>4
so in my opinion each statement answers the question
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02 May 2006, 03:28
fighter wrote:
ywilfred wrote:
2) If x is positive, is x>3?

a) (x-1)^2>4
b) (x-1)^2>9

St1:
(x-1)^2 - 4 > 0
(x-1+2)(x-1-2) > 0
(x+1)(x-3) >

Solving the first satement you get x<-1or x>3
The Question gives you the information that x is positive so x cant be less than -1 so x>3.
solving second equation x<-2 or x>4
but x cant be <-2 because x is positive so x>4
so in my opinion each statement answers the question

ah yes !! I missed the positive part. Thanks for pointing that out, your reasoning is correct.
Manager
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02 May 2006, 03:57
Thanks guys, OA is D.

Can you please tell me exactly when the inequality sign flips? I thought it was only when both sides are multiplied or divided by a negative number. Here are are subtracting, then why are we flipping the sign
Manager
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02 May 2006, 07:20
ywilfred wrote:
3) n, m are positive intergers. What is the remainder when 3^(4n+2) is divided by 10?
St2: knowing m is useless as we do not have the variable m in the equation.

Ans A

Question 3):

Consider the questions where they ask about the units digit of a product
of powers.

3^1 = 3 (mod 10)
3^2 = 9 (mod 10)
3^3 = 7 (mod 10)
3^4 = 1 (mod 10)
3^5 = 3 (mod 10)
3^6 = 9 (mod 10)
3^7 = 7 (mod 10)
3^8 = 1 (mod 10)
and so on.

So 3^(4n+2) = 9 (mod 10), no matter what n.

But it's the only question in DS I ever saw where the
answer could be given without any of the two statements.
This one was apparently meant to confuse us and choose A.
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02 May 2006, 09:00
Guys the OA for Question 3 is B! That's the surprising bit. I had marked A as well.
Manager
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02 May 2006, 09:24
Loner wrote:
Guys the OA for Question 3 is B! That's the surprising bit. I had marked A as well.

Well that's certainly not true, cause if n=2, the remainder can easily
determined since no variable is left.
02 May 2006, 09:24
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