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

Redeem

Algebra!

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Senior | Next Rank: 100 Posts
Posts: 74
Joined: Wed Apr 06, 2011 8:35 pm
Followed by:1 members

Algebra!

by Ahmed MS » Sat Oct 29, 2011 5:42 pm
Q: If XY+Z=X(Y+Z), then which of the following must be true?

1. X=0,Z=0
2. X=1,Y=1
3. Y=1,Z=0
4. X=1, Y=0
5. X=1,Z=0

OA is 5.
Very simple problem but I got confused. Please help me guys!


Cheers!
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 385
Joined: Fri Sep 23, 2011 9:02 pm
Thanked: 62 times
Followed by:6 members

by user123321 » Sat Oct 29, 2011 6:51 pm
Ahmed MS wrote:Q: If XY+Z=X(Y+Z), then which of the following must be true?

1. X=0,Z=0
2. X=1,Y=1
3. Y=1,Z=0
4. X=1, Y=0
5. X=1,Z=0

OA is 5.
Very simple problem but I got confused. Please help me guys!


Cheers!
xy+z = xy + xz
z = xz
z(x-1) = 0
x=1 or z=0

user123321
Just started my preparation :D
Want to do it right the first time.
Top
User avatar
GMAT Instructor
Posts: 509
Joined: Wed Apr 21, 2010 1:08 pm
Location: Irvine, CA
Thanked: 199 times
Followed by:85 members
GMAT Score:750

by tpr-becky » Sun Oct 30, 2011 8:23 am
if xy + z = x(y + z) you have to apply the distributive rule to get xy + z = xy + xz.subtract out the xy to get z = xz.

The only way for z to equal xz is if z = 0 or x = 1

The answers are written confusingly here- it is clear that the comma is supposed to be an "or" but without that clarification the problem is difficult to answer.
Becky
Master GMAT Instructor
The Princeton Review
Irvine, CA
Top
Post new topic Post Reply
• Page 1 of 1