amitgovin
The positive integers x, y, and z are such that x is a factor of y and y is a factor of z. Is z even?
(1) xz is even
(2) y is even.
Given:
x is a factor of y --> \(y=mx\), for some non-zero integer \(m\);
y is a factor of z --> \(z=ny\), for some non-zero integer \(n\);
So, \(z=mnx\).
Question: is z even? Note that \(z\) will be even if either \(x\) or \(y\) is even
(1) \(xz\) even --> either \(z\) even, so the answer is directly YES or \(x\) is even (or both). But if \(x\) is even and as \(z=mnx\) then z must be even too (one of the multiples of z is even, so z is even too). Sufficient.
(2) \(y\) even --> as \(z=ny\) then as one of the multiples of z even --> z even. Sufficient.
Answer: D.
Why z cannot be 3 or another odd nomrber for the 1 statement z=3 and x=2 will be even too.