DS Triangle : GMAT Data Sufficiency (DS)

DS Triangle

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DS Triangle [#permalink]

16 Aug 2008, 11:32

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Re: DS Triangle [#permalink]

16 Aug 2008, 12:19

C.

(1) Is insufficient because even though ABD = 60 degrees, there is not thing that indicates the opposite angle, ACD is also 60 degrees. The only way we could know this is if we knew that ABD is 60 degrees and the length of BD = DC. Without knowing that each triangle (ABD and ACD) are identical and mirrored, (1) is INSUFFICIENT.

(2) INSUFFICIENT. With this information we can find the area length of DC and therefore find the area of the triangle on the right, but there is nothing in this statement that says the triangle on the left is a mirror, or identical to, the triangle on the right.

TOGETHER: SUFFICIENT. Because we know that the triangle on the right is a 1:\sqrt{3}:2 triangle, we know that the interior angles measure 30:60:90. Since we know which angle on the left is 60, we know that that the triangles are identical and we can now determine the area of the entire thing.

dishant007 wrote:

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Re: DS Triangle [#permalink]

16 Aug 2008, 13:26

dishant007 wrote:

Answers and explanations

1) angle ABD=60
Angle BAD =30
ABD right angle triangle ..
sides BD, AD, AB are in the ration 1:sqrt3:2.
AD is given, Can find the BD and area of triangle ABD.

There is not enough information to find the area of traing ADC.

Insuffcient

2) AC=12
AD=6SQRT(3)
ADC right angle traingle ---> We can calculate DC and then area of triangle ADC.

There is no suffcient information to find area of traing ABD

Combine 1 and 2

ABC area = area of ABD+ area of ADC.

C.
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Re: DS Triangle [#permalink]

16 Aug 2008, 18:59

Agree with two of you, I have just fallen in the trap. Thanks!
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Re: DS Triangle [#permalink] 16 Aug 2008, 18:59

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DS Triangle

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