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# DS: Triangle

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Senior Manager
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DS: Triangle [#permalink]  07 May 2005, 04:07
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(N/A)

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0% (00:00) correct 0% (00:00) wrong based on 0 sessions
I don't understand OA on this one.
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0022.jpg [ 26.29 KiB | Viewed 740 times ]

Director
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I am getting B as answer...let me know if that is right i would then explain
VP
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gmat2me2 wrote:
I am getting B as answer...let me know if that is right i would then explain

B = 90 degree

Angle ACB=60 degree, and angle CAB=30 degree,

Hence, the triangle must not be isosceles triangle.

A seems insufficient
VP
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gmat2me2 wrote:
I am getting B as answer...let me know if that is right i would then explain

Go for B

angle B = 90 degree

Angle ACB=60 degree, and angle CAB=30 degree,

Hence, the triangle must not be isosceles triangle.

(1) seems insufficient
Director
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B will disporve its not an isoceles triangle

Manager
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It has to be B because the second stmt shows that the triangle abc is not isoceles triangle.
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Subhen

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Another vote for B.

In A , the angles of triangle ABC are not known to be equal or not.
In B, the angles are known and are 30,60
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ash
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I'm crossing the bridge.........

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Re: DS: Triangle [#permalink]  07 May 2005, 18:47
mirhaque wrote:
I don't understand OA on this one.

1 is suff too.

This goes to prove that triangle abc is not isosceles
Director
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Re: DS: Triangle [#permalink]  07 May 2005, 20:57
mirhaque wrote:
mirhaque wrote:
I don't understand OA on this one.

1 is suff too.

This goes to prove that triangle abc is not isosceles

I dont think you can use that theorem here simply because angle A is shared between the triangles .

So your (2) in your explanation is a a doubt for me.
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Re: DS: Triangle [#permalink]  08 May 2005, 05:47
mirhaque wrote:
mirhaque wrote:
I don't understand OA on this one.

1 is suff too.

This goes to prove that triangle abc is not isosceles

I get your point now mirhaque. the external angle of ADC is angle B and that should be suffiecient enough to say that A is also sufficient.....
Senior Manager
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Re: DS: Triangle [#permalink]  08 May 2005, 07:06
gmat2me2 wrote:
mirhaque wrote:
mirhaque wrote:
I don't understand OA on this one.

1 is suff too.

This goes to prove that triangle abc is not isosceles

I get your point now mirhaque. the external angle of ADC is angle B and that should be suffiecient enough to say that A is also sufficient.....

A is not sufficient.
I don't understand how you guys got A sufficient. B should be the answer.
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triangle.jpg [ 10.15 KiB | Viewed 688 times ]

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ash
________________________
I'm crossing the bridge.........

Director
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Re: DS: Triangle [#permalink]  08 May 2005, 08:22
ashkg wrote:
gmat2me2 wrote:
mirhaque wrote:
mirhaque wrote:
I don't understand OA on this one.

1 is suff too.

This goes to prove that triangle abc is not isosceles

I get your point now mirhaque. the external angle of ADC is angle B and that should be suffiecient enough to say that A is also sufficient.....

A is not sufficient.
I don't understand how you guys got A sufficient. B should be the answer.

Well the theorem the external angle of a triangle is equal to the sum of opposite angles is used here.

let acb = 2x while ADC = x

since ACB=2x ==>> ACD=180-2x

In triangle ACD angles A + D +C =180

So we have C =180-2x D =x So angle A for ACD has to be x.

So it is isoceles
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Re: DS: Triangle [#permalink]  08 May 2005, 08:54
gmat2me2 wrote:
ashkg wrote:
gmat2me2 wrote:
mirhaque wrote:
mirhaque wrote:
I don't understand OA on this one.

1 is suff too.

This goes to prove that triangle abc is not isosceles

I get your point now mirhaque. the external angle of ADC is angle B and that should be suffiecient enough to say that A is also sufficient.....

A is not sufficient.
I don't understand how you guys got A sufficient. B should be the answer.

Well the theorem the external angle of a triangle is equal to the sum of opposite angles is used here.

let acb = 2x while ADC = x

since ACB=2x ==>> ACD=180-2x

In triangle ACD angles A + D +C =180

So we have C =180-2x D =x So angle A for ACD has to be x.

So it is isoceles

The question is asking if trianlge ABC isosceles and not ACD.
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ash
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I'm crossing the bridge.........

Director
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Looks I have drifted to the other triangle :-D

Anyway ...As per the question B would be enough.......Thanks ashkg.....
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For 1), if you draw a isoceles triangle with B a right angle and BA=BC, then you draw a nother isoceles triangle where AC=AD, then 1) would be satisfied. However you can also draw a right triangle ABC where BA<>BC, and then still draw a triangle where AC=AD to satisfy 1). In other words 1) is not sufficient to determine whether ABC is isoleles.
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