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geometry - length

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geometry - length

by Xbond » Mon Aug 03, 2009 10:45 pm
Hi there,

I woud like your input about this difficult geometry question. Someone can explain to me in simple way the concept. Sorry, I don't know the answer. Look at the attachment

In triangle ABC above, what is the length of side BC ?
(1) The measure of angle AD has length 6.
(2) x = 36
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Re: geometry - length

by real2008 » Wed Aug 05, 2009 12:14 am
Xbond wrote:Hi there,

I woud like your input about this difficult geometry question. Someone can explain to me in simple way the concept. Sorry, I don't know the answer. Look at the attachment

In triangle ABC above, what is the length of side BC ?
(1) The measure of angle AD has length 6.
(2) x = 36
what do u mean by
(1) The measure of angle AD has length 6.
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by belize » Wed Aug 05, 2009 9:22 am
I came up with A as the answer.

from the diagram,
Angle ABC = 180-x-2x = 180-3x
Angle DBC = 180-2x-2x = 180-4x
so, Angle ABD = ABC - DBC = (180-3x) - (180-4x) = x
since ABD = BAD = x, side BD = AD
since BDC = BCD = 2x, side BD = BC
combining these two, side BC = BD = AD

Statement (1) gives AD = 6, so BC = AD = 6
eliminate choice B, C, and E

Statement (2) gives only the degree of the angles, which can prove that Angle B = C = 72 degree, but that doesn't provide the length of BC
eliminate choice D

Answer is A. Is this correct?
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by Xbond » Sun Aug 09, 2009 8:55 am
sorry, in statement 1, you have to read "the measure of segment AD has lenght 6. the right answer is A
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