Perimeter: what is it, how to calculate it, formula and examples

Category: Educational Model

What is the perimeter?

Perimeter is the measurement obtained as a result of the sum of the sides of a flat geometric figure. That is, the perimeter is what the contour of the figure measures.

The term perimeter comes from the Greek περίμετρος, a word made up of the prefix περί (peri), which means around and μετρος (metronome) which means measure.

Perimeter is also a word used in military jargon to refer to a high-security space.

How to remove the perimeter

To calculate the perimeter of a geometric figure it is necessary to know two basic variables:

  • The number of sides of the figure.
  • The length of each of those sides.

In the case of the circumference, it is necessary to know the length of the radius or its diameter in order to calculate its perimeter.

Perimeter formulas

These are the formulas to calculate the perimeter of some basic geometric figures:

Perimeter of Scalene triangle

A scalene triangle is one that has three unequal sides. The formula to calculate the perimeter of a scalene triangle it is:

P = a + b + c

where a, b and c are each of the sides.

A example of perimeter in a triangle scalene whose sides measure 3, 4 and 12 cm, it would be:

P = 3 + 4 + 12

P = 19 cm.

Perimeter of Isosceles triangle

An isosceles triangle is one that has two equal sides. The formula to calculate the perimeter of an isosceles triangle in this case it would be:

P = 2xl + b

A example of perimeter in an isosceles triangle, whose sides measure 37, 37 and 15 cm, would be:

P = 2×37 + 15

P = 74 + 15

P = 89 cm.

Perimeter of Equilateral triangle

The equilateral triangle is one that has three equal sides. The equilateral triangle perimeter formula it is:

P = 3xl

A example of perimeter in an equilateral triangle whose sides measure 9 cm, would be:

P = 3×9

P = 27 cm.

Perimeter of Square

A square is a flat geometric figure that has four equal sides. The formula to calculate the perimeter of a square it is:

P = 4xl

A example of perimeter in a square whose sides measure 7.5 cm, would be:

P = 4×7.5 cm.

P = 30 cm.

Perimeter of Rectangle

A rectangle is a flat geometric figure that has four sides with two different measurements (height and width). The formula to calculate the perimeter of a rectangle it is:

P = 2x (a + b)

A example of perimeter in a rectangle whose sides measure 2 and 8 cm respectively, it would be:

P = 2x (2 + 8)

P = 2x (10)

P = 20 cm.

Circumference

A circumference is a flat, closed curved line formed by points that are equidistant from the center. circumference perimeter formula it is:

P = 2π. r

A example of perimeter of a circumference whose radius measures 7.47 cm, would be:

P = 2x (3.14) x 7.47

P = 6.28x 7.47

P = 46.91 cm.