wieseljonas wrote:
Is \(x^2*y^3*z>0?\)
(1) yz>0
(2) xz<0
The official answer from Gmat Club is C.
I strongly think the correct answer is A and here is why:
From statement 1 y & z have the same sign wither both - or both +. This mean that the part of the equation given \(y^3*z\) is positive. And since \(x^\) has to be positive we can conclude that statement 1 is sufficient.
For me answer is A
What do you think?
Cheers
Is \(x^2*y^3*z>0\)?Inequality \(x^2*y^3*z>0\) to be true:
1. \(y\) and \(z\) must be either both positive or both negative, so they must have the same sign (in this case \(y^3*z\) will be positive);
AND
2. \(x\) must not be zero (in this case \(x^2\) will be positive).
(1) \(yz>0\). From this statement it follows that \(y\) and \(z\) are either both positive or both negative, so the first condition is satisfied. But we don't know about \(x\) (the second condition). Not sufficient.
(2) \(xz<0\). From this statement it follows that \(x\neq{0}\), so the second condition is satisfied. Don't know about the signs of \(y\) and \(z\) (the first condition). Not sufficient.
(1)+(2) Both conditions are satisfied. Sufficient.
Answer: C.
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