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Re: BD is parallel to AE. [#permalink]
Thank you.
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Re: BD is parallel to AE. [#permalink]
I don't understand.
CA could be different length than CE

Can anyone explain? Thank you
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Re: BD is parallel to AE. [#permalink]
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pclawong wrote:
I don't understand.
CA could be different length than CE

Can anyone explain? Thank you


\(\frac{{CB}}{{CA}} = \frac{{CD}}{{CE}}\) because they are similar and the ratio's of there length has to be equal.


CA= x+w (total length of CA, x & w are given)

CE = y+z (total length of CE, y & z are given)
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Re: BD is parallel to AE. [#permalink]
pranab01 wrote:
Pria wrote:
Explain Please



Here given BD is parallel to AE,

so angle CBD = angle CAE, and angle BDC = angle AEC.

Therefore the triangles BCD and ACE are similar (Angle C is common to both triangles and by AAA triangle BCD and triangle ACE are similar)

Now it is given side BC = x , AB = y and AC =x+w.

side CD = y, DE = z and CE = y+Z


Now as both triangles BCD and ACE are similar

therfore we have

\(\frac{CB}{CA}\) = \(\frac{CD}{CE}\)

substitute the values we get

\(\frac{x}{(x+w)}\)= \(\frac{y}{(y+z)}\)

or x(y+z) = y(x+w)

or xy + xz = xy + wy

or xz = wy. So option C.


If you put the reason, it will be better---

If two triangles are similar, the ratio of their corresponding sides are equal.

---------------------------------------------------------------------------------------------------------
Please let me know, if I am wrong.
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Re: BD is parallel to AE. [#permalink]
thank you
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Re: BD is parallel to AE. [#permalink]
pclawong wrote:
I don't understand.
CA could be different length than CE

Can anyone explain? Thank you

By maintaining ratio, any length is possible.
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Re: BD is parallel to AE. [#permalink]
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A line drawn parallel to a side of the triangle divides the two other sides proportionally. So x/w and y/z have the same ratio. Hence xz and wy are equal
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Re: BD is parallel to AE. [#permalink]
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Hi,

This is a question of proportionality of sides of two triangles that are similar. The larger and the smaller triangles are similar due to two common angles.

Here, x/w=y/z

So, xz=wy.

Hence, option (C) is the right answer.
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Re: BD is parallel to AE. [#permalink]
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Let's say x = a*w where 'a' is the constant term of proportionality between a side of the little triangle and the corresponding side of the larger triangle.
Then, it must be also that: y = a*z.

Therefore:
x*z = (a*w)*z
w*y = w*(a*z)

The two are equal, hence C.
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Re: BD is parallel to AE. [#permalink]
grewhiz wrote:
Hi,

This is a question of proportionality of sides of two triangles that are similar. The larger and the smaller triangles are similar due to two common angles.

Here, x/w=y/z

So, xz=wy.

Hence, option (C) is the right answer.



Can we reliably predict this relation? I thought the only relation we can predict from the diagram is x/(x+w) = y/(y+z)
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Re: BD is parallel to AE. [#permalink]
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Re: BD is parallel to AE. [#permalink]
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