OG Ed.11 DS # 117

[ifairo]

Please help me with your answer. If this problem has already been posted, then please refer me to the link.

Thanks.[/img]

[sachinkr]

As per question, Angle BDC = Angle BCD = 2x, therefore BC = BD.

Statement 1: AD = 6,
Angle ADB = 180-2x , so sum of Angle BAD and Angle ABD = 2x, but we cannot assume these two angles to be equal. So AD may not be equal BC. Therefore this statement is insufficient.

Statement 2: x=36, just knowing the angle would not help in determining the length of any side in this question. therefore insufficient.

Even with both the statements, we cannot get the length of BC.
Therefore (E). what is the OA?

[ifairo]

I am not convinced why A should be right. If you guys believe this is, indeed, a right answer, then please explain.

Regards.

[Brent@GMATPrepNow]

Please help me with your answer. If this problem has already been posted, then please refer me to the link.

Thanks.[/img]

I agree, the answer here must be E.
We could take point A and move it either left or right. Doing so would still allow triangle BDC to remain an isosceles triangle with angles 2x, 2x and 180-4x. However, moving point A around, would ruin any chances that triangle ADB is the isosceles triangle that the solution seems to suggest.

[logitech]

Question is not complete. In the original question there is more info!

[Ian Stewart]

Question is not complete. In the original question there is more info!

Exactly; in the original version of the question, angle DAB is labeled in the diagram; it measures x degrees. Then the answer is A. With the diagram in the original post, as pointed out above, the answer is clearly E.