### GMAT Challenge Problem Showdown: September 9, 2013

We invite you to test your GMAT knowledge for a chance to win! Each week, we will post a new Challenge Problem for you to attempt. If you submit the correct answer, you will be entered into that week’s drawing for a free Manhattan GMAT Prep item. Tell your friends to get out their scrap paper and start solving!

Here is this week’s problem:

A semicircular piece of paper has center

O, as shown above. Its diameterA’Ais coated with adhesive. If the adhesive is used to fuse radiiOA’andOAalong their entire lengths (so that pointsAandA’ coincide, pointsPandP’ coincide, and so on), a cone is formed as shown above. If pointBdivides the original semicircle into two identical arcs, what is the measure of angleAOBin the folded cone?

To see the answer choices, and to submit your answer, visit our Challenge Problem Showdown page on our site.

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The weekly winner, drawn from among all the correct submissions, will receive One Year of Access to our Challenge Problem Archive, AND the GMAT Navigator, AND Our Six Computer Adaptive Tests ($92 value).

answer is 90 degree