DS Question.. GmatPrep1

xunil56 wrote: IF xyz > 0 then, is x > 0?

1) xy > 0
2) xz > 0

Can you explain why OA is C?

xyz > 0 x>0?

statement (1)
xy>0
x could be negative, then y has to be negative
x could be positive, then y has to be positive.
Insufficient.

statement (2)
xz>0
same as above we can have both the cases of positive and negative.
Insufficient.

combining (1) & (2)
xz>0
xy>0

if x is negative, y and z both have to be negative, but then xyz> 0 will not hold true.

Therefore, x is positive. Sufficient.

Thus, C is the answer.