Even from elementary school, many people remember how to find the perimeter of any geometric figure: just find out the length of all its sides and find their sum. The perimeter is the total length of the boundaries of a flat figure. In other words, it is the sum of the lengths of its sides. The unit of measurement of the perimeter must match the unit of measurement of its sides. The formula for the perimeter of a polygon is P \u003d a + b + c … + n, where P is the perimeter, but a, b, c and n are the length of each of the sides. Otherwise, the circumference (or perimeter of a circle) is calculated: the formula p=2πr is used, where r is the radius, and π is a constant number, approximately equal to 3.14. Consider a few simple examples that clearly demonstrate how to find the perimeter. As an example, let's take such shapes 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 with all sides and angles equal. Since all sides of a square are equal, the sum of the lengths of its sides can be calculated using the formula P=4a, 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 \u003d 416.5 \u003d 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 a 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. Given a rectangle with one side 15 cm long and the other side set to 5 cm wide, we get a perimeter equal to P=2(15 + 5)=40 cm.
How to find the perimeter of a triangle
A triangle is formed by three segments that join at points (triangle vertices) that do not lie on the same line. A triangle is called equilateral if all three of its 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 \u003d 3a, where a is one of its sides. If the sides of the triangle are not equal to each other, it is necessary to carry out the addition operation: P \u003d 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
Parallelogram is a quadrilateral with pairwise parallel opposite sides. Square, rhombus and rectangle arespecial cases of the figure. The opposite sides of any parallelogram are equal, therefore, to calculate its perimeter, we use the formula P \u003d 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
Circle is a closed straight line, all points of which are located at equal distance from the center. The circumference of a circle and its diameter always have the same ratio. This ratio is expressed as a constant, written with the letter π and equals approximately 3.14159. You can find out the perimeter of a circle by multiplying the radius by 2 and by π. It turns out that the circumference of a circle with a radius of 15 cm will be equal to Р=23, 1415915=94, 2477
