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# if BD=DA, wath is angle BAO

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Manager
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if BD=DA, wath is angle BAO [#permalink]  16 Apr 2011, 23:10
00:00

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Question Stats:

0% (00:00) correct 100% (02:24) wrong based on 3 sessions
hello
so hard geometry question...
i can't solve it...
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Manager
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Re: if BD=DA, wath is angle BAO [#permalink]  17 Apr 2011, 08:30
Manager
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Re: if BD=DA, wath is angle BAO [#permalink]  17 Apr 2011, 13:14
No other info. The lines cannot be tangent either hah! b'coz that makes the ans 30, which isn't once of the choices.
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Last edited by ravsg on 17 Apr 2011, 15:20, edited 3 times in total.
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Re: if BD=DA, wath is angle BAO [#permalink]  17 Apr 2011, 13:43
1
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diebeatsthegmat wrote:

D and E make the sum of angles of OBD more than 180. So cannot be D and E.
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Re: if BD=DA, wath is angle BAO [#permalink]  17 Apr 2011, 22:32
is there NO body to help me?
i waiting 4 ur solutions! plz help!!!
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Re: if BD=DA, wath is angle BAO [#permalink]  17 Apr 2011, 22:59
I guess answer is B or C.

Let me eliminate the other choices. Lets consider the possibility angle BAO >= 45. Let angle BAO be x

angle BDO = 2x = angle OBD. If x = 45 then angle BDO is 2*45 = 90. Hence OBD cannot have two right angles. So we can eliminate D and E.

We can eliminate x = 15 since it is too small. I rely on my eyes since this is a PS. The only options left are B or C.

B Vs C
------
C. Lets assume x = 33. Then angle BOD is 180 - 4*33 = 180 - 132 = 48

B. Lets assume x = 38. Then angle BOD is 180 - 4*38 = 180 - 152 = 28

Now look at the figure. BOC = 2 * angle BOD. Do you think angle BOC can be greater than 90 deg? I doubt that. Hence I will guess B
Manager
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 09:45
the dia says, "not drawn to scale" so guesswork may not work and there should be a mathematical way to arrive at the ans, if at all.

Posted from my mobile device
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 21:01
gmat1220 wrote:
I guess answer is B or C.

Let me eliminate the other choices. Lets consider the possibility angle BAO >= 45. Let angle BAO be x

angle BDO = 2x = angle OBD. If x = 45 then angle BDO is 2*45 = 90. Hence OBD cannot have two right angles. So we can eliminate D and E.

We can eliminate x = 15 since it is too small. I rely on my eyes since this is a PS. The only options left are B or C.

B Vs C
------
C. Lets assume x = 33. Then angle BOD is 180 - 4*33 = 180 - 132 = 48

B. Lets assume x = 38. Then angle BOD is 180 - 4*38 = 180 - 152 = 28

Now look at the figure. BOC = 2 * angle BOD. Do you think angle BOC can be greater than 90 deg? I doubt that. Hence I will guess B

the dia says, "not drawn to scale" so guesswork may not work and there should be a mathematical way to arrive at the ans, if at all.
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 21:02
meprarth wrote:
Its 60 right?

Refer to the post above.
D and E make the sum of angles of OBD more than 180. So cannot be D and E.
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 21:12
I believe all not drawn to scale problems are DS.
You can trust your eyes if any PS geometry appears and somehow you are not able to solve it. you eyeball some options by merely looking at the shape or size. This may not be the best of allies but considering the time crunch it is.

ravsg wrote:
the dia says, "not drawn to scale" so guesswork may not work and there should be a mathematical way to arrive at the ans, if at all.

Posted from my mobile device

Posted from my mobile device
Manager
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 21:25
gmat1220 wrote:
I believe all not drawn to scale problems are DS.
You can trust your eyes if any PS geometry appears and somehow you are not able to solve it. you eyeball some options by merely looking at the shape or size. This may not be the best of allies but considering the time crunch it is.

ravsg wrote:
the dia says, "not drawn to scale" so guesswork may not work and there should be a mathematical way to arrive at the ans, if at all.

Posted from my mobile device

Posted from my mobile device

You are absolutely right about the time factor but here one has all the time one wants!
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 21:48
my solution :
OB=OD because those are circle's radius;
if BAO=A, then:
A=B2;
D1=B1;
D1+D2=180;
B2+A=D1 ==> B2+B2=B1 ==>2B2=B1
B1+B2=90 ;because BA is a tangent at B point
3B2=90 ==>B2=30==>A=30==>BAO=30
AM I WRONG???
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Re: if BD=DA, wath is angle BAO [#permalink]  18 Apr 2011, 21:52
annmary wrote:
my solution :
OB=OD because those are circle's radius;
if BAO=A, then:
A=B2;
D1=B1;
D1+D2=180;
B2+A=D1 ==> B2+B2=B1 ==>2B2=B1
B1+B2=90 ;because BA is a tangent at B point
3B2=90 ==>B2=30==>A=30==>BAO=30
AM I WRONG???

Looks good to me, I used the same to find out that 30 wasn't one of the choices.
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Re: if BD=DA, wath is angle BAO [#permalink]  24 Apr 2011, 01:13
i think these choices are wrong or shape is wrong
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Re: if BD=DA, wath is angle BAO [#permalink]  24 Apr 2011, 01:21
annmary wrote:
i think these choices are wrong or shape is wrong

What is the source?
VeritasPrep CAT, online course or VeritasPrep Guides?
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Re: if BD=DA, wath is angle BAO [#permalink]  24 Apr 2011, 04:55
fluke wrote:

What is the source?
VeritasPrep CAT, online course or VeritasPrep Guides?

I don't know, i found it in a web site!!!
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Last edited by annmary on 24 Apr 2011, 07:23, edited 1 time in total.
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Re: if BD=DA, wath is angle BAO [#permalink]  24 Apr 2011, 05:55
annmary wrote:
fluke wrote:

What is the source?
VeritasPrep CAT, online course or VeritasPrep Guides?

I don't know, i find it in a web site!!!

Can't do much about it then. Please don't waste time on this.
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Re: if BD=DA, wath is angle BAO [#permalink]  24 Apr 2011, 07:25
all right fluke!
thanks all so much ...
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Re: if BD=DA, wath is angle BAO   [#permalink] 24 Apr 2011, 07:25
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