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Condition X integer

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by karthikpandian19 » Wed Jan 04, 2012 9:20 pm
If x is an integer and x (x^0.5) - x = a ,
which of the following must be true?
I. a is Even
II. a is Positive
III. a is an Integer
A. I only
B. II only
C. III only
D. I and II
E. None of the above
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Source: — Data Sufficiency |
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by rijul007 » Wed Jan 04, 2012 10:45 pm
karthikpandian19 wrote:If x is an integer and x (x^0.5) - x = a , which of the following must be true?
I. a is Even
II. a is Positive
III. a is an Integer
A. I only
B. II only
C. III only
D. I and II
E. None of the above
Case 1:
If x = 1
x (x^0.5) - x = a
1(1) - 1 = a
a = 0

Statements III eliminated

Case 2:
If x = 2
x (x^0.5) - x = a
2(1.4) - 2 = a
0.8 = a

Statement I and II eliminated

Option E
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by ameya85 » Thu Jan 05, 2012 2:11 am
karthikpandian19 wrote: Case 2:
If x = 2
x (x^0.5) - x = a
2(1.4) - 2 = a
0.8 = a

Statement I and II eliminated
Can you please tell me how did you determine 2^.5 = 1.4? Is there any method to find this out?

Ameya
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by LalaB » Thu Jan 05, 2012 11:24 am
ameya85 wrote:
Can you please tell me how did you determine 2^.5 = 1.4? Is there any method to find this out?

Ameya
sqroot of 2=1.41
u should know it by heart

as fot the stmnt II. a is Positive, u can apply x=1 and get x (x^0.5) - x = a a=0. since 0 is neither positive, nor negative, u can reject stmnt II
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by ameya85 » Thu Jan 05, 2012 11:52 am
I somehow confused it with powers and roots. n^0.5 is the square root then n^-1 is also??? Sorry, It's been quiet a sometime I have lost math touch that's why asking such silly questions.

Ameya
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by LalaB » Thu Jan 05, 2012 11:55 am
ameya85 wrote:I somehow confused it with powers and roots. n^0.5 is the square root then n^-1 is also??? Sorry, It's been quiet a sometime I have lost math touch that's why asking such silly questions.

Ameya
n^0.5=n^(1/2)=sqroot of n

n^-1= 1/n

n^-2=1/n^2

everything is ok. we are all here to help each other :)
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by karthikpandian19 » Thu Jan 05, 2012 6:32 pm
OA is E
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