How to find the perimeter of a polygon?

Even from primary school, many remember how to find the perimeter of any geometric figure: it is enough to know the length of all its sides and find their sum. A perimeter is the total length of the boundaries of a plane figure. In other words, this is the sum of the lengths of its sides. The unit of measurement of the perimeter must correspond to the unit of measurement of its sides. The formula for the perimeter of a polygon has the form P = a + b + c ... + n, where P is the perimeter, and here a, b, c and n are the lengths of each side. Otherwise, the length of the circle (or perimeter of the circle) is calculated: the formula p = 2 * π * r is used, where r is the radius and π is a constant number of approximately 3.14. Let's look at some simple examples that clearly show how to find the perimeter. As a sample, we take such figures as a square, a rectangle, a triangle, a parallelogram, and a circle.

How to find the perimeter of a square

A square is a regular quadrilateral, in which all sides and angles are equal. Since all sides of the square are equal, the sum of the lengths of its sides can be calculated by the formula P = 4 * a, where a is the length of one of the sides. Thus, the perimeter of a square with a side of 16.5 cm is P = 4 * 16.5 = 66 cm. You can also calculate the perimeter of an equilateral rhombus.

How to find the perimeter of a rectangle

A rectangle is a quadrilateral with all angles equal to 90 degrees. It is known that in such a figure as a rectangle, the lengths of the sides are equal in pairs. If the width and height of the rectangle are the same length, then it is called a square. Usually the length of a rectangle is called the largest of the sides, and the width is the smallest. Thus, to get the perimeter of a rectangle, you need to double the sum of its width and height: P = 2 * (a + b), where a is the height and b is the width. Having a rectangle, one side of which is 15 cm long and the other of width with the set value of 5 cm, we get a perimeter equal to P = 2 * (15 + 5) = 40 cm.

How to find the perimeter of a triangle

The triangle is formed by three segments that connect at points (vertices of a triangle) that do not lie on the same straight line. A triangle is said to be equilateral, if all its three sides are equal, and is isosceles if there are two sides equal. To find out the perimeter of an equilateral triangle, it is necessary to multiply the length of its side by 3: P = 3 * a, where a is one of its sides. If the sides of the triangle are not equal to each other, it is necessary to perform the addition operation: P = a + b + c. The perimeter of an isosceles triangle with sides 33, 33 and 44, respectively, will be: P = 33 + 33 + 44 = 110 cm.

How to find the perimeter of a parallelogram

A parallelogram is a quadrilateral with pairwise parallel opposite sides. A square, a rhombus and a rectangle are particular cases of a figure. The opposite sides of any parallelogram are equal, so to calculate its perimeter we use the formula P = 2 (a + b). In a parallelogram with sides of 16 cm and 17 cm, the sum of the sides, or perimeter, is P = 2 * (16 + 17) = 66 cm.

How to find the circumference of a circle

A circle is a closed line, all points of which are located at an equal distance from the center. The circumference and its diameter always have the same ratio. This ratio is expressed by a constant, written using the letter π and is approximately 3.14159. The perimeter of a circle can be found from the product of the radius by 2 and by π. It turns out that the length of a circle with a radius of 15 cm will be equal to P = 2 * 3.14159 * 15 = 94.2477