Perimeter

From Encyclopedia Jr, free information reference for Kids

This article is about the distance around an object. For the freeway around Atlanta, Georgia, see Interstate 285.

The perimeter is the distance around a given two-dimensional object. The word perimeter is a Greek root meaning measure around, or literally "around measure."

[edit] Practical uses

Perimeter and area play a great role in today's world. Perimeter is used in calculating the border of an object such as a yard or flowerbed when a fence or other border is being installed around the edges. Area is used when all the area inside of a perimeter is being covered with something, such as a yard being covered with sod or fertilizer.

[edit] Formulas

[edit] Polygons

As a general rule, the perimeter of a polygon can always be calculated by adding all the length of the sides together. So, the formula for triangles is P = a + b + c, where a, b and c stand for each side of it. For quadrilaterals the equation is P = a + b + c + d. For equilateral polygons, P = na, where n is the number of sides and a is the side length.

[edit] Circles

For circles the equation is

or

• P stands for the perimter,
• r stands for the radius
• π is the mathematical constant pi (π = 3.14159265...)
• d stands for the circle's diameter (twice the radius of a circle)

(The dot means multiply or times)

[edit] See also

• Isoperimetric Theorem
• Circumference
• Pythagorean Theorem
• Wetted perimeter