153 - 159 Arithmetic Properties and Inequalities - The Beat The GMAT Forum

153 - 159 Arithmetic Properties and Inequalities

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phoenix9801: Master | Next Rank: 500 Posts; Posts: 190; Joined: Thu Jan 14, 2010 8:29 pm; Thanked: 2 times

by phoenix9801 » Tue Jul 13, 2010 3:49 pm

152- If x is an integer is x IxI < 2^x

(1) x < 0

(2) x = -10

note: the answer is D. , but I am having trouble to understand what is the question is asking? Can someone please explain in the simplest way and in depth please and how you would solve both statements.

159 - x < 0, is Y > 0 ?

(1) x/y < 0

(2) y-x > 0

Note : Is there any way you can solve this by using picking numbers or any other that is very simple please???

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Source: Beat The GMAT — Data Sufficiency | Tue Jul 13, 2010 3:49 pm

selango: Legendary Member; Posts: 1460; Joined: Tue Dec 29, 2009 1:28 amFollowed by: 7 members; Thanked: 135 times

by selango » Tue Jul 13, 2010 10:05 pm

159 - x < 0, is Y > 0 ?

(1) x/y < 0

(2) y-x > 0

x<0

y>0?

From stmt1,

x/y<0

Since x<0,y must be greater than 0 to satisfy the inequality.

Sufficient.

From stmt2,

y-x>0

y>x

x=-2,y=1,y>0

x=-2,y=-1,y<0

Insuffcient.

Hence A

--Anand--

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selango: Legendary Member; Posts: 1460; Joined: Tue Dec 29, 2009 1:28 amFollowed by: 7 members; Thanked: 135 times

by selango » Tue Jul 13, 2010 10:11 pm

152- If x is an integer is x IxI < 2^x

(1) x < 0

(2) x = -10

x*|x|<2^x

If x<0,x*(-x)<2^x=x^2>-2^x

If x>0,x^2<2^x

From stmt1,

x<0

So x^2>-2^x

Sufficient.

From stmt2,

x=-10

-10*10<2^10

100>1/2^10

Sufficient.

Hence D

--Anand--

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aloneontheedge: Senior | Next Rank: 100 Posts; Posts: 97; Joined: Thu Jan 28, 2010 2:07 am; Thanked: 9 times

by aloneontheedge » Thu Jul 29, 2010 10:20 am

selango wrote:
159 - x < 0, is Y > 0 ?

(1) x/y < 0

(2) y-x > 0

x<0

y>0?

From stmt1,

x/y<0

Since x<0,y must be greater than 0 to satisfy the inequality.

Sufficient.

From stmt2,

y-x>0

y>x

x=-2,y=1,y>0

x=-2,y=-1,y<0

Insuffcient.

Hence A

Selango,
Am i reading the question wrong?
it says -x < 0 which means x is positive
stmnt 1 : x/y < 0
since x is positive, y must be negative -->Suff
stmnt 2: y-x > 0 y>x
since x is positive y has to be positive --> Suff
Hence D

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aleph777: Master | Next Rank: 500 Posts; Posts: 131; Joined: Fri Jun 18, 2010 10:19 am; Location: New York, NY; Thanked: 10 times

by aleph777 » Thu Jul 29, 2010 10:42 am

Selango,

I misread that ' - ' as a negative sign at first, too. It's just how phoenix separated the question from the problem, though. You'll notice the same marking for the first question listed.

So the question simply reads:

x < 0, is y > 0?

and in that case, statement 1 is suf and 2 is insuf.

[/quote]

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aloneontheedge: Senior | Next Rank: 100 Posts; Posts: 97; Joined: Thu Jan 28, 2010 2:07 am; Thanked: 9 times

by aloneontheedge » Thu Jul 29, 2010 10:48 am

aleph777 wrote:Selango,

I misread that ' - ' as a negative sign at first, too. It's just how phoenix separated the question from the problem, though. You'll notice the same marking for the first question listed.

So the question simply reads:

x < 0, is y > 0?

and in that case, statement 1 is suf and 2 is insuf.

[/quote]
I agree.
A is the answer.
what a misinterpretation!!!!

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