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Kaplan Geometry DS: Is angle DFE = 60 degree?

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Kaplan Geometry DS: Is angle DFE = 60 degree?  [#permalink]

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New post Updated on: 01 Sep 2018, 22:47
1
Official answer is E, but I chose C.
What I wonder is, if EG bisects DF, shouldnt the triangle be an isoscles triangle? and if angle EDF is 60, i thought it would be equilaterial.
But the explanation says if EDF is 60 degrees, DEF can be 90 degrees and and DFE 30, so the answer is E. But I think in this case EG cannot bisect DF?

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Originally posted by minana on 01 Sep 2018, 20:08.
Last edited by minana on 01 Sep 2018, 22:47, edited 1 time in total.
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Re: Kaplan Geometry DS: Is angle DFE = 60 degree?  [#permalink]

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New post 01 Sep 2018, 21:45
minana wrote:
Official answer is D, but I chose C.
What I wonder is, if EG bisects DF, shouldnt the triangle be an isoscles triangle? and if angle EDF is 60, i thought it would be equilaterial.
But the explanation says if EDF is 60 degrees, DEF can be 90 degrees and and DFE 30, so the answer is E. But I think in this case EG cannot bisect DF?

Posted from my mobile device



If statement 1 says EG bisects DF, then there is no reason not to believe this.
Take these statements (1 and 2 ) in DS questions as facts

Let us come to the question .

When EG bisects DF say at point O , the only information we have is that DO=OF
we do not have any information on the angles

statement 1 is insufficient


statement 2 says EDF = 60

again on its own statement 2 is insufficient.
the other two angles E+F=120 , and can take various values



using both the statements

DO=OF and EDF=60
We still cannot ascertain the value of DFE

so the answer should be E
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Re: Kaplan Geometry DS: Is angle DFE = 60 degree?  [#permalink]

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New post 01 Sep 2018, 21:50
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Ohhh so bisecting doesnt have to be perpendicular.. I feel so dumb now, just couldnt see it myself ?
Thank you so much!

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Re: Kaplan Geometry DS: Is angle DFE = 60 degree?  [#permalink]

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New post 01 Sep 2018, 22:12
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minana wrote:
Official answer is D, but I chose C.
What I wonder is, if EG bisects DF, shouldnt the triangle be an isoscles triangle? and if angle EDF is 60, i thought it would be equilaterial.
But the explanation says if EDF is 60 degrees, DEF can be 90 degrees and and DFE 30, so the answer is E. But I think in this case EG cannot bisect DF?

Posted from my mobile device


Hi minana,

The question nowhere mentions that line EG is a perpendicular Bisector of DF. Consider line EG bisecting DF at some angle suppose 60. Had it been mentioned as a Perpendicular Bisector, then DE = EF. Hence, E.

Hope, this is clear.
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Re: Kaplan Geometry DS: Is angle DFE = 60 degree? &nbs [#permalink] 01 Sep 2018, 22:12
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Kaplan Geometry DS: Is angle DFE = 60 degree?

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