Even from elementary school, many remember how to find the perimeter of any geometric figure: it is enough to find out the length of all its sides and find their sum. The perimeter is the total length of the borders of a flat figure. In other words, this is the sum of the lengths of its sides. The unit of measurement of the perimeter should correspond to the unit of measurement of its sides. The perimeter formula of the polygon has the form P = a + b + c ... + n, where P is the perimeter, but a, b, c and n are the lengths of each side. Otherwise, the circumference (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 approximately equal to 3.14. Let's look at a few simple examples that demonstrate 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 quadrangle with all sides and angles 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 quadrangle with all angles equal to 90 degrees. It is known that in a figure such 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 the rectangle is called the largest of the sides, and the width is the smallest. Thus, in order to obtain the perimeter of a rectangle, it is necessary 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 with a width 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 the triangle) that do not lie on the same line. A triangle is called equilateral if all three sides are equal, and isosceles if there are two equal sides. 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, it is necessary to carry out the addition operation: P = a + b + c. The perimeter of an isosceles triangle with sides 33, 33 and 44, respectively, will be equal to: P = 33 + 33 + 44 = 110 cm.
How to find the perimeter of a parallelogram
A parallelogram is a quadrangle with pairwise parallel opposite sides. A square, a rhombus and a rectangle are special cases of a figure. The opposite sides of any parallelogram are equal, therefore, 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
The 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, is written using the letter π and is approximately 3.14159. You can find out the perimeter of a circle by the product of the radius by 2 and π. It turns out that the circumference with a radius of 15 cm will be equal to P = 2 * 3.14159 * 15 = 94.2477