IMO C
1: z*f > 0
z,f <0 or z,f > 0 Not suff
2: z+f > 0
z,f> 0 or one of them can be -ve. Not Suff.
Combine 1 and 2 both have to be +ve then only z*f > 0 and z+f > 0
thus right to zero.
DS
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Source: Beat The GMAT — Data Sufficiency |
- selango
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stmt1,
The product of Z and F is positive
This means Z&F are both negative or both postive.
Insuff
stmt2,
The sum of Z and F is positive.
There are 3 scenarios in this case.
Z=+ve,F=+ve-->Z&F are both right of 0
Z=-ve,F=+ve,F+Z=+ve-->Only F is right of 0
Z=+ve,F=-ve,F+Z=+ve-->Only Z is right of 0
Insuff
Combining 1 and 2,
To satisfy both conditions,Z and F must be both positive.
Suff
Pick C
The product of Z and F is positive
This means Z&F are both negative or both postive.
Insuff
stmt2,
The sum of Z and F is positive.
There are 3 scenarios in this case.
Z=+ve,F=+ve-->Z&F are both right of 0
Z=-ve,F=+ve,F+Z=+ve-->Only F is right of 0
Z=+ve,F=-ve,F+Z=+ve-->Only Z is right of 0
Insuff
Combining 1 and 2,
To satisfy both conditions,Z and F must be both positive.
Suff
Pick C
--Anand--
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clock60
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here my answer is C
(1) f*z>0 possible in two cases
f>0 z>0, ( both to the right of zero), or
f<0, z<0 (both to the left of 0), so 1 st insuff
(2) also insuff (f+z)>0 if
f>0, z>0,-here to the right of 0
but it can be that f>0, z<0 and sum also +ve (2+(-1)=1
also insuff
both st are valid for z>0, f>0, so suff
(1) f*z>0 possible in two cases
f>0 z>0, ( both to the right of zero), or
f<0, z<0 (both to the left of 0), so 1 st insuff
(2) also insuff (f+z)>0 if
f>0, z>0,-here to the right of 0
but it can be that f>0, z<0 and sum also +ve (2+(-1)=1
also insuff
both st are valid for z>0, f>0, so suff












