6th Class Mathematics Mensuration Mensuration (Perimeter & Area, Review of Earlier Concepts)

MENSURATION

(Perimeter and Area, Review of Earlier Concepts)

     FUNDAMENTALS

•                         Area is the part of plane occupied by the closed figure.

(a) Perimeter of a square \[=4\,\,\times \]side.

Elementary question-1: Find perimeter of a square kabaddi field each of whose side is 20 metres Ans. Perimeter \[4\times 20=80\,\,m\]

(b) Perimeter of a rectangle \[=2\times \] (length + breadth) units.

(c) Area of a square = (side \[\times \] side).

(d) Area of a rectangle = length \[\times \] breadth.

(e) Area of a parallelogram = base \[\times \] height sq. units.

(f) Area of a triangle \[=\frac{1}{2}\] (Area of the parallelogram generated from it)

\[=\frac{1}{2}\times \]base \[\times \] height sq. units

•                      If the length of sides of a triangle are a, b, c and \[s=\frac{a+b+c}{2}=\] half perimeter, then area is given as\[\Delta =\sqrt{s\left( s-a \right)\left( s-b \right)\left( s-c \right)}\]
•                      Circumference of a Circle: The perimeter of a circle is called its circumference.

Circumference \[=2\pi r=\pi d,\] where \[r=\]radius and \[d=\]diameter.

Here \[\pi \,\,(Pi)\] is a constant, equal to\[3.14\]     approximately.

•                       Area of a circle: Area of a circle with radius r units is equal to \[\pi {{r}^{2}}sq\]units.