Data Sufficiency

Is the product of A and B equal to 1?

(1) ABA = A
(2) BAB= B

ans:E

ab=1?

St 1 aba = a

If a=0, then aba=a=0 Hence the answer to the ques is no
If a & b are both not equal to zero then aba = a; ab = 1 ----answer to the ques is yes.

hence this statement alone is INSUFF

St 2 bab = b

Same reasoning as above----INSUFF

Combining 1 & 2
You have the same problem either both a & b=0 or both can be equal to 1 in both the cases we don't have a definite yes/no reply to the ques

hence the answer is E

I just want to add a tip

Every time you see an equation in the form of AB=A always remember you can NEVER cancel out the two As because A can be equal to 0 as well (unless mentioned its a non 0 integer). That's a very common trap in GMAT.

Thanks, I was doing the same mistake. will remember in future.

mals24 wrote:I just want to add a tip

Every time you see an equation in the form of AB=A always remember you can NEVER cancel out the two As because A can be equal to 0 as well (unless mentioned its a non 0 integer). That's a very common trap in GMAT.