Introduction to Perimeter,Circumference and Area

Perimeter

The perimeter of a polygon is the distance around the outside of the polygon. A polygon is 2-dimensional; however, perimeter is 1-dimensional and is measured in linear units. To help us make this distinction, We can think about a rectangular backyard. The yard is 2-dimensional: it has a length and a width. The amount of fence needed to enclose the backyard (perimeter) is 1-dimensional. The perimeter of this yard is the distance around the outside of the yard, indicated by the red arrow; It is measured in linear units such as feet or meters.

• To find the perimeter of a polygon, take the sum of the length of each side.
• To find the perimeter of a polygon, take the sum of the length of each side. The formula for perimeter of a rectangle is:P=2·L+2·W. To find the perimeter of a regular polygon, multiply the number of sides by the length of one side.
• The perimeter of a parallelogram is the distance around the outside of the parallelogram. A parallelogram has four sides with opposite sides being congruent. The formula for finding the perimeter is Side A + Side B + Side A + Side B. This could also be stated as 2*Side A + 2*Side B or 2*(Side A + Side B).

Area

• The area of a shape is a number that tells how many square units are needed to cover the shape. Area can be measured in different units, such as square feet, square meters, or square inches.
• You can find an area by drawing a shape on graph paper, and counting the squares inside the shape. But this is not very practical, so we use area formulas instead. Every polygon and circle has a formula for finding its area.
• Area of a rectangle A = bh
• Area of a square A = side²
• Area of a triangle A = 1/2bh
• Area of a parallelogram A = bh
• Area of a circle = r²
• Area of a rhombus = bh
• Area of a trapezoid =1/2(a+b)h

Circumference of circles

The circumference of a circle is the actual length around the circle which is equal to 360°. Pi (p) is the number needed to compute the circumference of the circle.

p is equal to 3.14. Pi is greek and has been around for over 2000 years!

• In circles the AREA is equal to 3.14 (p) times the radius (r) to the power of 2.

   Thus the formula looks like: A= pr2.

• In circles the circumference is 3.14 (p) times the Diameter.

   Thus the formula looks like: 2pr or pd.