In parallelogram KLMN above, 4 is the height when LM or KN is used as the base. Base × height = 6 × 4
= 24.
Remember that to find the area of a parallelogram you need the height, which is the perpendicular
distance from the base to the opposite side. You can use a side of a parallelogram for the height only
when the side is perpendicular to the base, in which case you have a rectangle.
Rectangles: A rectangle is a four-sided figure with four right angles. Opposite sides are equal.
Diagonals are equal. The perimeter of a rectangle is equal to the sum of the lengths of the four sides,
which is equal to 2(length + width).
Area of Rectangle = length × widthThe area of a 7-by-3 rectangle is 7 × 3 = 21.
Rhombus: A rhombus is a four-sided figure with four equal sides.
All four sides of the quadrilateral above have the same length, so it’s a rhombus. A rhombus is also a
parallelogram, so to find the area of a rhombus, you need its height. The more a rhombus “leans
over,” the smaller the height and therefore the smaller the area. The maximum area for a rhombus