Dissecting a parallelogram to a rectangle

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Drag the point marked "Move cut-off piece" to rearrange the pieces to a rectangle.

You can change:

the location of the cut on the parallelogram
the height of the parallelogram
the base of the parallelogram (A or B)
the shape of the parallelogram (A, B, and/or D)

The slider for moving the cut-off piece can be moved to directly measure the base of the parallelogram and rectangle.
The outlined rectangle can be moved to compare directly to other objects.

Questions

How are the base and height of the parallelogram related to the base and height of the resulting rectangle?

The area of the rectangle is A = bh. What is a formula for the area of the parallelogram?

If you cut the parallelogram along a diagonal into two triangles, what is the area of one of the triangles?

What happens to the area if you slide the top side of the rectangle along a line parallel to the base?

For some parallelograms, the cut line only cuts off a small triangle, and the resulting shape is not a rectangle. How could you deal with parallelograms like this?

Susan Addington, Created with GeoGebra

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