Data Sufficiency

sparkle6 wrote:What is the value of (x^2)*y*z + x*(y^2)*z + x*y*(z^2)
1) x+y+z = 18
2) xyz = 10
[spoiler]Answer: C[/spoiler]

First factor the given expression to rewrite the target question as: What is the value of (xyz)(x+y+z)?

Statement 1: x+y+z = 18
Does this allow us to find the value of (xyz)(x+y+z)?
No. It tells us the value of the blue portion of the expression, but not the red portion.
As such, statement 1 is not sufficient.

Statement 2: xyz = 10
Does this allow us to find the value of (xyz)(x+y+z)?
No. It tells us the value of the red portion of the expression, but not the blue portion.
As such, statement 2 is not sufficient.

Statements 1 & 2:
Does this allow us to find the value of (xyz)(x+y+z)?
Yes. It tells us the value of the blue portion of the expression and the value of the red portion.
As such, statements 1+2 are sufficient, and the answer is C.

Cheers,
Brent