Data Sufficiency

hi jbsears,
did u follow what mr. Rahul said?
BAC is x.
that solves all problem. the q published & file uploaded here on d web site therefore must have been incorrect.
with Rahuls INFO ans. is A.
agree with FEI:)

aim-wsc,

Rahul's answer is right if that is true but it is not. The OG doesn't give the angle BAC is X. Therefore, one cannot assume it is X. Maybe there are alternative versions of the book, but the book I have doesn't have BAC listed as X. So the answer is E. But if it was X, then A would be the correct answer.

phew... glad I found this.. I was going cross-eyed reading the explanation in the OG which wasn't making any sense to me..

They've missed a vital bit of information while printing it... It must be stated that BAC is x, or half of BDC, or something.

It's kinda dissappointing actually.. Giving 'sufficient' data is most critical in the Data Sufficiency section..

There is a same question in OG10 with extra information. With the information given in OG 10, the correct answer is absolutely A, but without it, the correct answer is E.

can somebody explain how by giving /BAD as X we can get the ans with A alone???????????

One thing I can tell here is andle BCA = 2x. Now this (interior angle) will be equal to the sum of the two exterior angles that is angle ABC + angle ADC. Probably this is how OG is telling angle ABD is x.

okay i struggled enuf on this to solve, finally it all boils down to this one theorem:

An exterior angle of a triangle is equal in measure to the sum of the two non-adjacent interior angles of the triangle


1. since <BDC=<BCD ==> BD=BC
2. now apply the above theorem to triangle BAD ==> <BDC = <BAC + <ABD

2x=x+y ==> x=y

3. Since, x=y implies that "side AD= side DB= side BC"

4. it is given in option A that AD=6 ==> side BC=6

5. Hence answer is A