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

Redeem

Can anyone solve this question from GMAT Prep?

This topic has expert replies
Post new topic Post Reply
Previous Topic Next Topic
Newbie | Next Rank: 10 Posts
Posts: 8
Joined: Sat Jun 16, 2007 7:47 am

Can anyone solve this question from GMAT Prep?

by charmingirl8 » Sun Sep 02, 2007 9:01 am
Hello All! This question showed up on my GMAT Practice Test 1, from GMAT Prep Software sent to us when we sign up for the test...Is anyone able to solve this and show me the path to the right answer? The answer makes no sense to me...Thanks!

*i'll publish the answer later...

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 and y=0
e- x=1 and z=0
Top
Source: — Problem Solving |
Master | Next Rank: 500 Posts
Posts: 214
Joined: Fri Jul 20, 2007 1:35 am
Thanked: 3 times

Re: Can anyone solve this question from GMAT Prep?

by beny » Sun Sep 02, 2007 11:04 am
Distribute the right side:
xy+z = xy+xz

Cancel the xy from both sides:
z = xz

In order for this to be true, either x=1 (z=z) or z=0 (0=0).

Therefore, the answer is E.
Top
Newbie | Next Rank: 10 Posts
Posts: 8
Joined: Sat Jun 16, 2007 7:47 am

by charmingirl8 » Sun Sep 02, 2007 1:43 pm
thanks Beny! You got it right...and it makes sense now!
Top
Junior | Next Rank: 30 Posts
Posts: 17
Joined: Wed Jan 24, 2007 3:35 am

Another view

by amitamit2020 » Mon Sep 03, 2007 12:27 am
But ans (e) states : x = 1 "AND" z = 0 -- however the explaination given concludes x=1 "OR" z = 0 . Thus to satisfy equation z = xz both the conditions need not to satisfy however ans (e) implies that. I think the only condition that MUST be true is (a) i.e. x = 0 "AND" z = 0.

Any comments please.
Top
Junior | Next Rank: 30 Posts
Posts: 24
Joined: Wed Aug 22, 2007 4:49 pm
Thanked: 3 times

Re: Another view

by jaspreet.sharma » Mon Sep 03, 2007 11:32 pm
amitamit2020 wrote:But ans (e) states : x = 1 "AND" z = 0 -- however the explaination given concludes x=1 "OR" z = 0 . Thus to satisfy equation z = xz both the conditions need not to satisfy however ans (e) implies that. I think the only condition that MUST be true is (a) i.e. x = 0 "AND" z = 0.

Any comments please.
A cant be the answer as

ATQ z=xz

If x=0 this means z too is 0 or 1 or 2.....or can be any number

So value of Z cant be determined.

So answer is z=0 and x=1
Top
Master | Next Rank: 500 Posts
Posts: 258
Joined: Mon Aug 27, 2007 12:43 pm
Thanked: 15 times

by ri2007 » Wed Sep 05, 2007 6:58 pm
I got the same equation z = xz

but I dont understand why X and Z both cannot be 0 ?

I agree if x=1 and z=0 the equation is satisfied, but cant understand why choice A does not work.

Would appreciate if some one could explain.

thanks a lot
Top
Legendary Member
Posts: 645
Joined: Wed Sep 05, 2007 4:37 am
Location: India
Thanked: 34 times
Followed by:5 members

by camitava » Thu Sep 06, 2007 1:50 am
Yop I think we r all at the equation : z = xz. Now as pointed out by amitamit2020 (a very good observation u can say!), the option E is having "AND" with it. But tell me one thing amitamit2020 - is it not satisfying the equation now if z = 0 and x = 1? But with option A, we are putting a controversy about "Is 0 multiplied by 0 1?" So I think Jaspreet is right! What do u say guys?
:shock: Correct me if I am wrong :( :D
Correct me If I am wrong


Regards,

Amitava
Top
Master | Next Rank: 500 Posts
Posts: 101
Joined: Tue Aug 07, 2007 1:45 am
Followed by:1 members

by agps » Thu Sep 06, 2007 2:10 am
we all agree that the equation simplifies to z =x*z

if x=1 z=z and z can be any value, not necessairly 0

if x=0 z must be 0, or else the equation is false.

try out in the original equation
if x=1
XY+Z= X(Y+Z) results in
y+z=y+z
0 = 0, regardless of the value of Z so E can't be right, even if z were 999 the equation would hold true.

if x=0
XY+Z= X(Y+Z) results in
z=0
therefore the answer should be A x=0 and z=0

charmingirl8 already stated that the OA is E, but it makes no sense to me. what is the origin of this question?
Top
User avatar
Legendary Member
Posts: 986
Joined: Wed Dec 20, 2006 11:07 am
Location: India
Thanked: 51 times
Followed by:1 members

by gabriel » Thu Sep 06, 2007 5:14 am
agps wrote:we all agree that the equation simplifies to z =x*z

if x=1 z=z and z can be any value, not necessairly 0

if x=0 z must be 0, or else the equation is false.

try out in the original equation
if x=1
XY+Z= X(Y+Z) results in
y+z=y+z
0 = 0, regardless of the value of Z so E can't be right, even if z were 999 the equation would hold true.

if x=0
XY+Z= X(Y+Z) results in
z=0
therefore the answer should be A x=0 and z=0

charmingirl8 already stated that the OA is E, but it makes no sense to me. what is the origin of this question?
that is because charmingirl8 has got the answer options wrong .. the ans is E and the the answer choice E says x=1 or z=0 ...

.. also people make a note that the question asks what "must be " true and not what "could be" true .. makes a huge difference...
Top
Post new topic Post Reply
• Page 1 of 1