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Re: In triangle ABC above, what is the lenght of side BC? 1) [#permalink]

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16 Jul 2007, 14:57

1

This post received KUDOS

Sorry, I did see it now.

The answer should be A.

We know from the figure that <BAC=x , <BDC=<BCD=2x
So BD=BC, since <BDC=<BAC+<ABD, this tells you <ABD=x as well.
Therefore, AD=BD, since we have already find out that BD=BC, so AD=BC. Statement 1 alone is sufficient.

Statement 2 tells you the value of X, but didn't tell you anything about the length of the segment, therefore is not sufficient.

Re: In triangle ABC above, what is the lenght of side BC? 1) [#permalink]

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23 Oct 2010, 15:12

Awesome Just one simple explanation for how <BDC = <BAC+<ABD, exterior angle in a triangle is the sum of the opposite interior angles. It took me a while to figure it out, may be helpful.

Concentration: General Management, Entrepreneurship

GMAT 1: 650 Q42 V37

GRE 1: 1310 Q630 V680

GPA: 3.16

Re: In triangle ABC above, what is the lenght of side BC? 1) [#permalink]

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22 Nov 2010, 09:17

I was going to pick A originally, but upon seeing that x=36 (I assumed that x should be 30), I felt no choice but to pick C.

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In triangle ABC above, what is the length of side BC?

Since <BDC = <BCD then the BD=BC. Also, since <ADB = 180 -2x (exterior angle) and the sum of the angles of a triangle is 180 degrees, then in triangle ADB we'll have: x + (180 - 2x) + <ABD = 180 --> <ABD = x. Now, we have that <ABD = x = <DAB so AD = BD --> AD = BD = BC.

Question: BC=?

(1) Line segment AD has length 6 --> AD = BD = BC = 6. Sufficient.

(2) x = 36 --> we know only angles which is insufficient to get the length of any line segment.