Parallelograms

Finding the area and perimeter of a parallelogram is exactly like a rectangle, with only a minor change.  Here is a parallelogram.

This looks like a squashed box.  The dashed line is called the height.  If you look, you could cut this into triangles.  With that being said, the bottom of a parallelogram is called the base.  Let's look at why we treat them like a rectangle.

If we cut the triangle off the left side, we can move it to the other side.

We can then push them together to make a rectangle.

Therefore, the formula is a = b x h.

If we have the following parallelogram, we would look like this:

                                a = b h

a = ?                        a = 9 cm (5 cm)

b = 9 cm                  a = 45 cm^2

h = 5 cm

Remember, the height MUST create a right angle to the base.  We do not use the slanted side unless we are talking about perimeter.