Square :

Perimeter of a Square = 4 $$\times$$ side of a square

Area of a Square = $$\text{(side of a square)}^{2}$$

Rectangle :

Perimeter of a Rectangle = 2(length+breadth)

Area of a Rectangle = length $$\times$$ breadth

Circle :

Diameter = $$2\times radius$$

Perimeter/Circumference of a Circle = $$2\times\pi\times radius$$

Area of a Circle = $$\pi \times (radius)^{2}$$

Right Angle Triangle:

Perimeter = hypotenuse+base+height

Area = $$\frac{1}{2}\times base \times height$$

Equilateral Triangle:

Perimeter = 3a

Area = $$\frac{\sqrt{3}}{4}\times a^{2}$$

Isosceles Triangle:

Perimeter = (2a+b)

Area = $$\frac{1}{2}\times b \times h$$

Scalene Triangle:

Perimeter = (a+b+c)

S = (a+b+c)/2

Area = $$\sqrt{S(S-a)(S-b)(S-c)}$$

Here a, b and c are the three sides of a triangle.

Note :: The sum of all the three angles of a triangle is equal to 180°.

Rhombus:

Perimeter = 4 $$\times$$ side

Area = $$\frac{1}{2}\times D_{1} \times D_{2}$$

Parallelogram:

Perimeter = $$2\times(l+b)$$

Area = $$b \times h$$

Trapezium:

Perimeter = p+q+r+s

Area = $$\frac{1}{2}\times h \times(p+r)$$