The circumference of a rectangle = (length+width) ×2 C=(a+b)×2.

Circumference of a square = side length ×4 C=4a

Area of rectangle = length× width S=ab

Area of a square = side length × side length s = a.a = a.

Area of triangle = base × height ÷2 S=ah÷2.

Area of parallelogram = base × height S=ah

Trapezoidal area = (upper bottom+lower bottom) × height ÷ 2s = (a+b) h ÷ 2.

Diameter = radius ×2 d=2r Radius = diameter ÷2 r= d÷2.

Circumference = π× diameter = π× radius× 2c = π d = 2π r

Area of circle = π× radius× radius

Area of triangle = base × height ÷2. The formula S= a×h÷2.

Square area = side length × side length formula S= a×a

Area of rectangle = length× width Formula S= a×b

Area of parallelogram = base× height Formula S= a×h

etc