| View previous topic :: View next topic |
| Author |
Message |
magical cook
GMAT Destroyer!
Joined: 30 Jul 2006
Posts: 484
Thanks given: 6
Thanked 1 times in 1 posts
|
 Posted: Tue Jan 22, 2008 9:35 pm Post subject: simple one |
 |
|
For any numbers a and b, a · b = a + b – ab.
If a · b = 0, which of the following CANNOT be a value of b?
(A) 2
(B) 1
(C) 0
(D) -1
(E) -2/3
simple but I got it wong... OA will follow. can you pls explain? |
|
| Back to top |
|
 |
|
|
simplyjat
GMAT Destroyer!
Joined: 27 Dec 2007
Posts: 422
Thanks given: 3
Thanked 30 times in 29 posts
Location: Hyderabad, India
Test Date: May 20, 2008
Target GMAT Score: 770
|
| Posted: Tue Jan 22, 2008 9:56 pm Post subject: |
|
|
The best way is to substitute all the answer choices for the value of B in A + B - AB = 0 and try to find out the value of A...
For the second answer choice we get
=> A + 1 - A = 0
=> 1 = 0
thus B cannot have a value 1.
_________________
simplyjat |
|
| Back to top |
|
|
sibbineni
Really wants to Beat The GMAT!
Joined: 04 Jan 2008
Posts: 223
Thanks given: 0
Thanked 15 times in 14 posts
|
| Posted: Wed Jan 23, 2008 2:46 am Post subject: |
|
|
IMO B
Given Data:
a.b=a+b-ab
a.b=0
Now substitute all the choices in a+b-ab=0 ---(1)(since a.b=0)
1---> option b =2 subtitiuting in the equation 1 we have a=2
2---> option b=1 in equation 1 we have 1=0 so b cannot have a value
3---> option b=0 in equation we have a=0
4-->option b=-1 we have a=1/2
5--->option b=-2/3 we have a=2/5
in the (B) case we dont have a value......
---------------------------------
Suggest me if Iam Wrong |
|
| Back to top |
|
|
|
