# Perimeter, perimeter formulas

**Perimeter** of a figure is the sum of the lengths of all sides.

Not all figures have perimeter, for example a ball(sphere) does not have a perimeter.

The standard notation for **perimeter in math** is the letter P

#### Perimeter of a square

Let's a square side is long a. Square have four equal sides
so **square perimeter** is P = a + a + a +a or:

#### Perimeter of a rectangle

Let's a rectangle sides are long a and b.

The length of all its sides is P = a + b + a + b or:

#### Perimeter of a parallelogram

Let's palallelogram sides are long a and b

The length of all its sides is P = a + b + a + b so parallelogram perimeter is:

As you can see the perimeter of the parallelogram is equal the perimeter of the rectangle.

#### Perimeter of an isosceles trapezoid

Say the length of the parallel sides of a trapezoid are long a and b and the other two sides are long c(As we know isosceles trapezoid has two equal sides).

#### Perimeter of an equilateral triangle

As we know equilateral triangles have 3 equal sides. So if the length of the side is a then the perimeter formula is P = a + a + a

#### Perimeter of a parallelepiped

Parallelepiped is a figure that all sides are parallelogram.(Rectangular parallelepipeds is a figure that sides are rectangles.)

If bottom edges are long a and
b then the perimeter of the bottom is P = 2a + 2b.
Every parallelepiped have two bottoms so the perimeter of the two bottoms is (2a + 2b).2 = 4a + 4b.
As we know parameter is sum of all edges. So we have to add four times c

#### Perimeter of a cube

Cube is a parallepiped that sides are squares(all edges are equal).

So the perimeter of a cube is the number of edges * length.

Every cube has 12 edges.

So the perimeter formula of a cube is: