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Does the product of A and B equal to 1 ? 1) A*B*A = A 2)

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Senior Manager
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Does the product of A and B equal to 1 ? 1) A*B*A = A 2) [#permalink] New post 23 Sep 2006, 08:26
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A
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C
D
E

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100% (01:53) correct 0% (00:00) wrong based on 0 sessions
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Does the product of A and B equal to 1 ?

1) A*B*A = A
2) B*A*B = B
VP
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 [#permalink] New post 23 Sep 2006, 08:43
Answer: E

S1. A^2B - A = 0

or A(AB-1) = 0

A = 0 OR AB = 1

If A = 0, then AB = 0
If AB=1, then AB = 1

Not sufficient.

S2: B^2A -B =0
B(AB-1) = 0

B=0, OR AB =1

If B=0, then AB=0
If AB=1, then AB=1
Not sufficient.

S1 & S2:
A =0 OR B=0 OR AB=1

If A=0 or B=0, then AB=0
If AB=1, then AB=1

Not sufficient.

Answer: E
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 [#permalink] New post 23 Sep 2006, 08:44
(E)

We have the case A=B=0 that remains, along with A=B=1.
SVP
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 [#permalink] New post 23 Sep 2006, 09:37
Does the product of A and B equal to 1 ?

1) A*B*A = A
2) B*A*B = B

FOR THE PRODUCT OF A,B TO EQUAL ONE

A=B=-1 OR A=B=1 OR THEY ARE RECEPROCALS

FROM ONE

A,B =1OR -1 OR A,B = ZERO.....INSUFF

FROM TWO

A,B = 1 OR -1 OR A,B = ZERO.....INSUFF

BOTH TOGETHER are insuff...my answer is E
Senior Manager
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 [#permalink] New post 23 Sep 2006, 18:17
Guys I am amazed at the speed all of you answer questions . Great going ...

Yup I got E too.
  [#permalink] 23 Sep 2006, 18:17
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Does the product of A and B equal to 1 ? 1) A*B*A = A 2)

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