Data Sufficiency

If z is a positive integer, is root z an integer?

1. Root (xz) is an integer
2. x = z^3

OA: E

HG10 wrote:If z is a positive integer, is root z an integer?

1. Root (xz) is an integer
2. x = z^3

OA: E

Part 1: sqrt(xz) is an integer

Examples make this easy...

x = 1 AND z = 4. sqrt(4) = 2
x = 2 and z = 2. sqrt(2) NOT an integer

INSUFFICIENT

Part 2: x = z^3

This puts no restrictions on z. INSUFFICIENT

(1) and (2)
Combining the formulas for parts 1 and 2, we get sqrt(z^4) is an integer, which again has no restriction on z, since z^2 of any integer is an integer.

INSUFFICIENT

E

Thanks for the solution!