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## Comment on

Triangles with Intersection## Hi Brent, can we conclude

Thanks for these videos, they are a great help!

Kai

## Hi Kai,

Hi Kai,

You are correct; AB and CD are parallel, because we're told that ∠ABC = ∠BCD

Cheers,

Brent

## Brent,

Could you explain me in a different way from the OG17 Solution. Exercise #138 OG17.

Thanks,

Pedro

## Hi Pedro,

Hi Pedro,

You'll find my step-by-step solution here: https://gmatclub.com/forum/figures-x-and-y-above-show-how-eight-identica...

Cheers,

Brent

## Hi Brent, Can we consider

## ∠BAD and ∠CDA aren't

∠BAD and ∠CDA aren't vertically opposite.

∠AEB and ∠CED are vertically opposite.

More here: https://www.gmatprepnow.com/module/gmat-geometry/video/858 (the part about vertically opposite angles starts at 4:20 in the video)

Cheers,

Brent

## hey brent, how do u know

thanks

Yianni

## Great question,Yianni!!

Great question,Yianni!!

As long as your ratios on each side have the same structure, EITHER equation works.

OPTION #1: We can have "(length of one side of BIG triangle)/(length of corresponding side of SMALL triangle) = (length of another side of BIG triangle)/(length of corresponding side of SMALL triangle)

In this case, we get: 12/5 = 10/x

When we solve this, we get: x = 25/6

-----------------------------

OPTION #2: We can have "(length of one side of SMALL triangle)/(length of corresponding side of BIG triangle) = (length of another side of SMALL triangle)/(length of corresponding side of BIG triangle)

In this case, we get: 5/12 = x/10

When we solve this, we still get: x = 25/6

Does that help?

Cheers,

Brent

## perfect! thanks a lot!

## https://gmatclub.com/forum/in

not able to solve this one

sir is this gmat level question?

## Here's my solution: https:/

Here's my solution: https://gmatclub.com/forum/in-triangle-abc-d-is-the-mid-point-of-bc-and-...

This is a crazy hard question. As I mention in my post, I'd say "skirting the 800 level of difficulty!"

Cheers,

Brent

## In the case of congruent

## I'm not sure whether you

I'm not sure whether you meant to say CONGRUENT or SIMILAR.

That said, there are many different ways for the test-maker to create two triangles that are similar (and congruent). Using parallel lines (as in the above video question) is just one of the ways.

Cheers,

Brent

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