Posted by Twg on .
The legs of an ironing board are equal in length and
bisect each other at the point where they cross.
What generalization about
parallelograms ensures that the ironing board will
always be parallel to the floor, regardless of the height
of the board above the floor?

GEOMETRY 
Ms. Sue,
What does "parallel" mean?

GEOMETRY 
Twg,
level to doesn't it?

GEOMETRY 
Ms. Sue,
A parallelogram has two sides that are the same distance apart. They are parallel  like this:
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Here's a site about parallelograms.
http://www.ies.co.jp/math/products/geo1/applets/para/para.html
I'm sure you'll be able to answer the question now. Please post your answer, and I'll be glad to check it. 
GEOMETRY 
Twg,
ok, is it because the legs are the same size??

GEOMETRY 
Ms. Sue,
Your question is: "What generalization about parallelograms ensures that the ironing board will always be parallel to the floor, regardless of the height
of the board above the floor?"
This part of the above site answer the question.
1. The opposite sides are equal in length.
. . .
3. The diagonals bisect each other. 
GEOMETRY 
Twg,
so the opposite legs are the same in length even though they cross each other. That's the answer?

GEOMETRY 
Ms. Sue,
The legs are diagonals of the parallelogram, and they bisect each other.