Numbers property Question

Question

Hey gang, does anyone know a systematic way to solve to following problem:


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) -3/2

Thanks for your help

Praetorian · Answer

did you mean, if ab not equal to 0

Roc-a-fella · Answer

Praet, 
ab is equal to 0, this question came from GMAT #55 paper ed.

Anonymous · Answer

Think it's B........!!
0=a+b+ab
=>a = b/b-1
Hence b cannot be 1 since that would yield 'a' as undefined..........!!

cbrf3 · Answer

Oops I forgot to login......BTW the equation shud be 0 = a+b-ab and that would yield a = b/b-1!!!

Emmanuel · Answer

B, of course:

if b = 1, then a + b - ab = 1 != 0.

GoalStanford · Answer

note a*b there is just notation (similar to those x bar probelms) and just means f(a,b).

B is corect.

Just substitue values and see if the solution contradicts any known stuff.

Numbers property Question

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