Area of a circle: The area of a circle is the region occupied by the circle in a two-dimensional plane.

Perimeter of a Triangle = 3 × length of a side.

Perimeter of a rectangle = 2 × length + 2 × breadth

P = 2(1 + b) ⇒ (i) l = `P/2` − b, i.e., length = `"Perimeter"/2` − breadth

                         (ii) l = `P/2` − l, i.e., breadth = `"Perimeter"/2` − length

Perimeter of Square = Total boundary of the square

                                   = Side + Side + Side + Side

P = 4 × Side

Or: P = 4s (where 's' represents the side length)

side = ` "perimeter"/"4"`

Always include the correct linear unit (cm, m, mm, km, etc.)

Area of the trapezium = `1/2` × sum of the lengths of parallel sides × height.

Area of parallelogram = base x height

• Area of a rhombus = `1/2` x product of lengths of diagonals.

Area of the circle = πr²