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GMATPrep geometry In the figure shown, point O is the center [#permalink]

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05 Nov 2006, 20:57

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GMATPrep geometry

In the figure shown, point O is the center of the semicircle and points B, C, and D lie on the semicircle. If the length of line segment AB is equal to the length of line segment OC, what is the degree measure of angle BAO?

(1) The degree measure of angle COD is 60

(2) The degree measure of angle BCO is 40

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Last edited by kidderek on 05 Nov 2006, 21:35, edited 1 time in total.

i can tell by your posts that you are very good in quant. you actually post explanations rather than restating the already posted OA.

1 question, at what point did you know that (1) is sufficient? Was it when you saw the information given, or did you have to play around with the diagram before it clicked in your head that it is SUFF?

i can tell by your posts that you are very good in quant. you actually post explanations rather than restating the already posted OA.

1 question, at what point did you know that (1) is sufficient? Was it when you saw the information given, or did you have to play around with the diagram before it clicked in your head that it is SUFF?

Thanks. It's hard to answer exactly. When I look at problems like this, I have a feel for how much structure there is in the problem and how much info I need. In this problem, I would have bet at very impressive odds that (1) was sufficient immediately.

I also got this question when I did my test prep, and the OA is D.

I got B orginally becuase I brought in the information from A.

What overall math score did you get?

If the question was for me, I also answered this question as B, b/c I couldn't do much with statement 1. I got 10 wrong on quant and got a 47, I believe (need to double check). Oddly, I had 18 DS questions instead of the normal 15 DS, which I think lowered my score.

I stink at DS, my hit rate fluctuates from 50% to 80%

i can tell by your posts that you are very good in quant. you actually post explanations rather than restating the already posted OA.

1 question, at what point did you know that (1) is sufficient? Was it when you saw the information given, or did you have to play around with the diagram before it clicked in your head that it is SUFF?

Good question kidderek. In fact I picked out the choice 2 quite easily using the same logic as you have used.

But at first glance wasn't yielding me the result. It was only when I did the calculation that I realized 1 is sufficient as well. I am pretty good in Geometry, but I just couldn't believe GMAT would need so much calculation..

There must be a shorter, quicker way of calculating this.

Remember that you don't have to calculate the answer; you just need to know that you can. Thus, if you just start labeling everything in terms of t, you will find that eventually you have an equation that amounts to solve for t. That makes it sufficient and go on.