Is xy + xz = 0

Anurag@Gurome: GMAT Instructor; Posts: 3835; Joined: Fri Apr 02, 2010 10:00 pm; Location: Milpitas, CA; Thanked: 1854 times; Followed by:523 members; GMAT Score:770

by Anurag@Gurome » Tue Apr 12, 2011 7:05 pm

moatik wrote:1) x = 0
2) y + z = 0

I get that first one is sufficient, but how is the second one?

Question: Is xy + xz = 0?

(1) x = 0 implies xy + xz = x(y + z) = 0(y + z) = 0
So, (1) is SUFFICIENT.

(2) y + z = 0 implies x(y + z) = x * 0 = 0
So, (2) is SUFFICIENT.

The correct answer is D.

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Stuart@KaplanGMAT: GMAT Instructor; Posts: 3225; Joined: Tue Jan 08, 2008 2:40 pm; Location: Toronto; Thanked: 1710 times; Followed by:614 members; GMAT Score:800

by Stuart@KaplanGMAT » Tue Apr 12, 2011 7:33 pm

moatik wrote:1) x = 0
2) y + z = 0

I get that first one is sufficient, but how is the second one?

The question becomes much simpler if you simplify the question!

Is xy + xz = 0?

Is x(y + z) = 0?

When will this be true? If x=0 or (y + z) = 0.

(1) x = 0... sufficient!
(2) y + z = 0... sufficient!

Each statement is sufficient alone - choose (D).

Stuart Kovinsky | Kaplan GMAT Faculty | Toronto

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