GMAT Prep?? (Factors)

dferm · Posted: Thu May 08, 2008 6:26 am Post subject: GMAT Prep?? (Factors)

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

Can someone please help me here...?

Thanks.

moneyman · Posted: Thu May 08, 2008 6:41 am Post subject:

Is it D?

dferm · Posted: Thu May 08, 2008 8:04 am Post subject:

AleksandrM · Posted: Thu May 08, 2008 10:43 am Post subject:

The foundation rule here is that if x is a factor of y and y is a factor of z then x is also a factor of z. Now, you also know that y is bigger than x and z is either bigger than xy or equals to it.

Statement one tells you that xz is even. This means that one of the numbers is even. However, you also know that x is a factor of y. So if x is 3 and y is 9, then z MUST be even, or 18, for example. Sufficient.

Statement two tells you that y is even. If y is 6 and x is any odd integer, when you multiply them together, the result is always even. Now, z can have other factors, and all of them can be odd. As long as one of the factors is even, z MUST be even. Sufficient.

Choose D.