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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