Perimeter: Square, Rectangle, Triangle, Polygons

Overview

**Perimeter ** :

Perimeter of a figure is the length of the line or curve forming the boundary of the figure.

Perimeter of square $=4\times \phantom{\rule{1ex}{0ex}}\text{side}$

Perimeter of rectangle $=2\times \phantom{\rule{1ex}{0ex}}\text{length + width}$

Perimeter of triangle $=\phantom{\rule{1ex}{0ex}}\text{sum of three sides}$

Perimeter of polygon $=\phantom{\rule{1ex}{0ex}}\text{sum of sides}$

perimeter

The measure of length is the "distance-span between two points".

Perimeter of a figure is the length of the line or curve forming the boundary of the figure.

The word "perimeter" means: measure around a shape.

Perimeter is from the Greek root words peri (around) and meter (measure).

The perimeter of a square of side $3$ cm is $3+3+3+3=4\times 3=12$ cm.
*Perimeter of a square is $4$ times the length of the side.*

The perimeter of a rectangle of length $6$ cm and width $4$ cm is $6+4+6+4=2\times (6+4)=20$ cm. *Perimeter of a rectangle is twice the sum of length and width.*

The perimeter of a triangle of sides $6$ cm, $5$ cm, and $4$ cm is $6+5+4=15$ cm. *The perimeter of a triangle is sum of the lengths of the three sides.*

The perimeter of a polygon of sides, $6$ cm, $2$ cm, $5$ cm, $4$ cm, and $6$ cm is $6+2+5+4+6=23$ cm. *Perimeter of a polygon is the sum of the lengths of its sides.*

examples

What is the perimeter of a equilateral triangle with sides, $1$cm?

The answer is "$1+1+1=3$ centimeter".

What is the perimeter of a rectangle formed by joining $2$ squares of side $3$ cm?

The answer is "$18$cm".

Two squares are joined and the rectangle has length $3+3=6$cm and height $3$cm.

So the perimeter is $2(6+3)=18$ cm.

What is the perimeter of regular pentagon of side $2$cm?

The answer is "$10$cm".

summary

**Perimeter ** :

Perimeter of a figure is the length of the line or curve forming the boundary of the figure.

Perimeter of square $=4\times \phantom{\rule{1ex}{0ex}}\text{side}$

Perimeter of rectangle $=2\times \phantom{\rule{1ex}{0ex}}\text{length + width}$

Perimeter of triangle $=\phantom{\rule{1ex}{0ex}}\text{sum of three sides}$

Perimeter of polygon $=\phantom{\rule{1ex}{0ex}}\text{sum of sides}$

Outline

The outline of material to learn "Mensuration basics : Length, Area, & Volume" is as follows.

Note: * click here for detailed outline of Mensuration (Basics). *

• ** Measuring Basics**

→ __Introduction to Standards__

→ __Measuring Length__

→ __Accurate & Approximate Meaures__

→ __Measuring Area__

→ __Measuring Volume__

→ __Conversion between Units of Measure__

• ** 2D shapes**

→ __Perimeter of Polygons__

→ __Area of Square & rectangle__

→ __Area of Triangle__

→ __Area of Polygons__

→ __Perimeter and area of a Circle__

→ __Perimeter & Area of Quadrilaterals__

• ** 3D shapes**

→ __Surface Area of Cube, Cuboid, Cylinder__

→ __Volume of Cube, Cuboid, Cylinder__