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October 21, 2014

October 21, 2014

Posted by **olav** on Sunday, December 12, 2010 at 11:58am.

A vertical line is drawn from the top to bottom called GH (between points AD and BC).

A line is drawn from left to right called EF (between points AB and GH).

AEFG is Rectangle 1.

EBHF is Rectangle 2.

GHCD is Rectangle 3.

All three rectangles are similar.

Length of line AE (vertical) is 4cm.

Length of line EB (vertical) is 9cm.

What is the area of rectangle GHCD ?

- Gr. 9 math -
**Reiny**, Sunday, December 12, 2010 at 12:38pmI did not answer this question before, because I found it confusing.

AEFG EBHF are not rectangles

Is there a point named for the intersection of GH and EF ?

Check your typing.

- Gr. 9 math -
**olav**, Sunday, December 12, 2010 at 1:49pmI don't see a problem but I will rewrite the structure.

Make two rectangles attached together.

Call the first rectangle ABHG (AG top, BH bottom).

Call the second rectangle GHCD (HC top, GD bottom).

Draw a horizontal line from line AB to line GH and name the points E on line AB and F on line GH.

example:

A----G-------------D

|....|.............|

|....|.............|

E----F.............|

|....|.............|

|....|.............|

|....|.............|

|....|.............|

B----H-------------C

Rectangles AEFG, EBHF and GHCD are similar.

The length of AE is 4cm.

The length of EB is 9cm.

What is the area of rectangle GHCD ?

- Gr. 9 math -
**Reiny**, Sunday, December 12, 2010 at 2:41pmLook at your diagram and trace out

figure AEFG, it does not form a rectangle.

the same is true for EBHF.

Also, it is proper notation to list the order of letters of similar shapes so that line segments correspond.

e.g.

If I were to say triangle ABC is similar to triangle PQR

then, without looking at the diagram, I can tell that

AB/AC = PQ/PR etc.

I think we have to call the intersection of EF and GH something like K

So did you mean rectangle AEKG is similar to rectangle EBHK ?

How do the sides line up?

I think it would have to be something like

AE/EK = EK/EB

- Gr. 9 math -
**olav**, Sunday, December 12, 2010 at 3:04pmI reposted a better structure at 1:58

thank you for your help so far.

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