Why It's E?! Please Explain.

BREAKING: Target Test Prep releases Brand New 2026 On Demand GMAT prep course

Redeem

This topic has expert replies

Post new topic Post Reply

Previous Topic Next Topic

Haitham: Newbie | Next Rank: 10 Posts; Posts: 2; Joined: Tue Apr 15, 2008 12:41 am

Why It's E?! Please Explain.

by Haitham » Tue Nov 18, 2008 5:07 pm

Hi all!

I need help understanding this question and its answer:

If xy+z=x(y+z), which of the following must be true?

A) x=0 and z=0
B) x=1 and y=1
C) y=1 and z=0
D) x=1 or y=0
E) x=1 or z=0

The correct answer is E, but why? (my first choice was A)

Thanks,
Haitham

Last edited by Haitham on Mon Dec 29, 2008 4:45 am, edited 1 time in total.

Quote

Source: Beat The GMAT — Problem Solving | Tue Nov 18, 2008 5:07 pm

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pm; Thanked: 331 times; Followed by:11 members

by cramya » Tue Nov 18, 2008 5:13 pm

Haitham,
Refer to https://www.beatthegmat.com/gmatprep-xy- ... 18211.html

Stuart provided a nice solution with explanation which may answer your question.

Let us know if u still have questions.

Quote

Ossa: GMAT Instructor; Posts: 30; Joined: Sun Oct 26, 2008 5:42 pm; Thanked: 5 times

Re: Why It's E?! Please Explain.

by Ossa » Tue Nov 18, 2008 6:13 pm

Hi Haitham,

I think this is the shortest way to do it:

If xy+z=x(y+z), then
xy+z=xy+xz, which means that xz=z, and this can only happen if x=1, or if z=0.

Haitham wrote:Hi all!

I need help understanding this question and its answer:

If xy+z=x(y+z), which of the following must be true?

A) x=0 and z=0
B) x=1 and y=1
C) y=1 and z=0
D) x=1 or y=0
E) x=1 or z=0

The correct answer is E, but why? (my first choice was A)

Thanks you,
Haitham