Thank you for using the timer - this advanced tool can estimate your performance and suggest more practice questions. We have subscribed you to Daily Prep Questions via email.

Customized for You

we will pick new questions that match your level based on your Timer History

Track Your Progress

every week, we’ll send you an estimated GMAT score based on your performance

Practice Pays

we will pick new questions that match your level based on your Timer History

Not interested in getting valuable practice questions and articles delivered to your email? No problem, unsubscribe here.

Thank you for using the timer!
We noticed you are actually not timing your practice. Click the START button first next time you use the timer.
There are many benefits to timing your practice, including:

condition I is sufficient (hard to explain without diagram, I'll post the diagram later), but angle BAO comes out to be 20

condition II is sufficient because:

Given that <BCO is 40, this means <CBO is also 40, since triangle BCO is isoceles (because the 2 radii are same).

Now <CBO and <ABO are supplementary, meaning they must add up to 180, so that leaves us <ABO = 140.

Finally, triangle ABO is also isoceles, because segment AB is the same as the radius. So that means each of the other 2 angles of triangle ABO is equal to 20

Statement 1: First of let us establish few things - BAO and BOC are iscoseles triangles. so angles BAO=BOA; OBC=OCB Given that COD=60. Assuming BOC=x BOA=180-x-60=120-x...1 also, OBC=(180-x)/2 => OBA = 180-(180-x)/2 => BOA=(180-OBA)/2= (180-(180-(180-x)/2)/2 = (180-x)/4...2 Equating 1 and 2 => 120-x=(180-x)/4 => 480-4x=180-x => x=100 => BAO=BOA=180-100-60=20 You really don't need to solve till the end in the exam, once you get a feel that you can solve for x you are pretty much done.

My answer is also D, similar to Sri's logic Triangles BOC & BOA are both isosceles triangles and hence have equal bases. Therefore you only need to determine one angle in triangle BOA. With statement 1, you can deduce angle BOA ( as triangle in the semi circle is a right angle trinangle; the other angle is provided by the statement and 180- both gives angle BOA). And since BOA=BAO, the statement is sufficient. Similarly with second statement you can get angle OBC, which will help deduce angle OBA. (180-angle OBA)/2 will be the solution.