A rectangle is a parallelogram containing four right angles. Opposite sides (a = c, b = d) are equal and the perimeter is the sum of the lengths of all sides (a + b + c + d) or, comonly, 2 x length x width. The area of a rectangle is length x width. A square is a rectangle with four equal length sides. The perimeter of a square is 4 x length of one side (4s) and the area is the length of one side squared (s^{2}).
Which of the following is not true about both rectangles and squares?
the area is length x width 

the lengths of all sides are equal 

the perimeter is the sum of the lengths of all four sides 

all interior angles are right angles 