Perimeter is the continuous line forming the boundary of a closed geometric figure(shape). Perimeter is often measured by measuring the outsides of a figure. Here are some commonly used equations for perimeter (x = multiplication):[br][br]Circle: 2 x π x radius[br]Rectangle: 2(l x w)[br]Square: 4 x a (a = sides)[br]Parallelogram: 2(a+b)[br]Triangle: a + b + c[br]Trapezoid: a + b + c + d[br]