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# GMAT SET 19

Author Message
Manager
Joined: 14 Jan 2006
Posts: 88
Schools: HKUST

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23 Sep 2008, 13:52

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Senior Manager
Joined: 18 Jun 2007
Posts: 274

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23 Sep 2008, 15:16
is 3x > 7y ?

St1 (x> y+4) suggests that 3x would be bigger than 7y only if y> 3
lets see why?
put x = y+4 into equation 3x > 7y
=> 3(y + 4)> 7y
=> 3y + 12 > 7y
=> 12 > 4y
=> 3 > y

you can check by putting values
St.1 insufficient

St2 tells us that 5x > 14 y
=> x is equal or bigger than 3y
=> if x is 3 y is 1
now put the values into equaltion 3x > 7y
x= 3, y= 1 => 3*3 > 7*1 ? ...........yes
x=9, y= 3 => 3*9 > 7*3 ?............yes

VP
Joined: 05 Jul 2008
Posts: 1337

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23 Sep 2008, 17:35
I am getting sufficicency in both cases but getting a N and Y . Either I must be wrong or the Q is wrong

Is 3x> 7y?

(1) says x-y > 4 and x, y both +ve

For any x, y values (1,6) (3,8) (4,8.5) (10,15) I got a N. Any thing I missed
(2) says -5x < -14y means 5x > 14 y -> x > 2.8y

If we substitute 2.81y for x in the given equation we see that 3x > 7y Y
Manager
Joined: 14 Jan 2006
Posts: 88
Schools: HKUST

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23 Sep 2008, 17:37
any more takers ???
Manager
Joined: 14 Jan 2006
Posts: 88
Schools: HKUST

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23 Sep 2008, 21:09
THE OA given is D...I think it should be B
VP
Joined: 17 Jun 2008
Posts: 1479

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25 Sep 2008, 12:49
icandy wrote:
I am getting sufficicency in both cases but getting a N and Y . Either I must be wrong or the Q is wrong

Is 3x> 7y?

(1) says x-y > 4 and x, y both +ve

For any x, y values (1,6) (3,8) (4,8.5) (10,15) I got a N. Any thing I missed
(2) says -5x < -14y means 5x > 14 y -> x > 2.8y

If we substitute 2.81y for x in the given equation we see that 3x > 7y Y

if x = 6 and y = 1 then 3x > 7y
But, if x = 15 and y = 10 then3x < 7y.

That is why, A cannot be sufficient.
Retired Moderator
Joined: 05 Jul 2006
Posts: 1734

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26 Sep 2008, 22:20
x,y are +ve

is 3x>7y

1) x> y+4
2)-5x 7y

3y+12>7y

12> 4y ie: 3>y substitute for y = 3 in the iniquality 1 , thus x >7

however y is a bit less than 3 and x a bit bigger than 7

thus 3(bit bigger than 7 ) > 7( a bit less than 3) ....suff

from 2

5x> 14y

2.5x> 7y

since x,y are positive then sure 3x>7y.......suff

--== Message from GMAT Club Team ==--

This is not a quality discussion. It has been retired.

If you would like to discuss this question please re-post it in the respective forum. Thank you!

To review the GMAT Club's Forums Posting Guidelines, please follow these links: Quantitative | Verbal Please note - we may remove posts that do not follow our posting guidelines. Thank you.
Re: GMAT SET 19   [#permalink] 26 Sep 2008, 22:20
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# GMAT SET 19

Moderator: chetan2u

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