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.