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# Arithmetics - not so difficult DS problem from VStudy

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Arithmetics - not so difficult DS problem from VStudy [#permalink]

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08 Jun 2004, 01:00
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- Guys,
I encountered into not so difficult DS problem. I guess that VStudy answersheet gives wrong answer. (Book 1, Test 1)

Is x(y+z)>0
(1) xyz>0
(2) yz>0
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08 Jun 2004, 02:44
Hi,

Lets look at the second statement...
yz>0 => Case 1: y -> +ve and z ->+ve
x could be either +ve or -ve so (B) is not sufficient
for same reason (1) is also not sufficient
Assuming (1) and (2) both... again y n z could be
either +ve or -ve which means (y+z) could be either
so we cannot tell as x could also be either

Case 2: y -> -ve and z ->ve
Same reasoning!

Hence we cannot say anything... answer (E)

Another approach would be to draw a table like this

X Y Z X(Y + Z)

Statement 1 1 -1 -1 -2
(No inference) -1 1 1 -2
-1 -1 -1 2

Statement 2 -1 -1 1 0
(No inference) 1 -1 -1 -2
1 1 1 1

The combined condition is also covered among the above sample data
and no inference is possible
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08 Jun 2004, 03:29
thanx, manan,

the table is really helpful.
Senior Manager
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08 Jun 2004, 06:58
my guess is C

from 2 we get y and z either + or - ve
from 1 we get either two of digits can be -ve and one can be +
so combine we get yz to be of same signs .
_________________

shubhangi

Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Technology, Entrepreneurship
GMAT 1: 710 Q49 V0
GMAT 2: 700 Q V
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 7: Q42 V44
GMAT 8: Q42 V44
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GMAT 10: 740 Q V
GMAT 11: 500 Q47 V33
GMAT 12: 670 Q V
WE: Engineering (Manufacturing)
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Re: Arithmetics - not so difficult DS problem from VStudy [#permalink]

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08 Jun 2004, 20:50
Solo wrote:
- Guys,
I encountered into not so difficult DS problem. I guess that VStudy answersheet gives wrong answer. (Book 1, Test 1)

Is x(y+z)>0
(1) xyz>0
(2) yz>0

A is not sufficient. For XYZ to be > 0, at least 2 variables has to be -ve or all 3 variables to be +ve.

B is also not sufficient. Both Y & Z can be -ve or +ve ( YZ must have same sign ) to get YZ> 0.

A & B together, let's look at condition with YZ> 0,
X Y Z YZ XYZ X(Y+Z)
1 2 3 6 6 6
1 -2 -3 6 6 -5

As you can see, X(Y+Z) can be +ve or -ve.

Thus, C is still not sufficient. The answer has to be E.
Joined: 31 Dec 1969
Location: Russian Federation
Concentration: Technology, Entrepreneurship
GMAT 1: 710 Q49 V0
GMAT 2: 700 Q V
GMAT 3: 740 Q40 V50
GMAT 4: 700 Q48 V38
GMAT 5: 710 Q45 V41
GMAT 6: 680 Q47 V36
GMAT 7: Q42 V44
GMAT 8: Q42 V44
GMAT 9: 740 Q49 V42
GMAT 10: 740 Q V
GMAT 11: 500 Q47 V33
GMAT 12: 670 Q V
WE: Engineering (Manufacturing)
Followers: 0

Kudos [?]: 202 [0], given: 102248

Re: Arithmetics - not so difficult DS problem from VStudy [#permalink]

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08 Jun 2004, 20:53
Solo wrote:
- Guys,
I encountered into not so difficult DS problem. I guess that VStudy answersheet gives wrong answer. (Book 1, Test 1)

Is x(y+z)>0
(1) xyz>0
(2) yz>0

A is not sufficient. For XYZ to be > 0, at least 2 variables has to be -ve or all 3 variables to be +ve.

B is also not sufficient. Both Y & Z can be -ve or +ve ( YZ must have same sign ) to get YZ> 0.

A & B together, let's look at condition with YZ> 0,
X Y Z YZ XYZ X(Y+Z)
1 2 3 6 6 6
1 -2 -3 6 6 -5

As you can see, X(Y+Z) can be +ve or -ve.

Thus, C is still not sufficient. The answer has to be E.
Intern
Joined: 06 May 2004
Posts: 17
Location: Queens, NY
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08 Jun 2004, 20:56
Ooops, forgot to sign my user name. It wasn't a guest.
08 Jun 2004, 20:56
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# Arithmetics - not so difficult DS problem from VStudy

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