Parallelogram

A parallelogram is a four-sided plane figure (quadrilateral) with two pairs of parallel sides. Thus a parallelogram is of the shape shown below.

A parallelogram has opposite sides equal.

The opposite angles of a parallelogram are equal

Two angles not opposite add to 180o

Note that rectangles, rhombuses and squares are all parallelograms.

A rectangle is a parallelogram with all angles equal.

A rhombus is a parallelogram with all sides equal.

A square is a parallelogram with all sides equal and all angles equal.

Therefore a square is both a rectangle and a rhombus.

The area of a parallelogram is found by multiplying the base length by the vertical height.

For example, in the above parallelogram, the length of the base is 8cm and the vertical height is 5cm. So the area is 40 cm2.

This result may be explored and discovered by students using paper parallelograms and cutting off a triangle from one side of the parallelogram and joining it to the other side to form a rectangle.