Calculating the Ratio of Perimeter to Area Understanding the Concepts

The perimeter of a shape is the measure of the length of a shape around its outermost extremities. The area of a shape is the amount of two-dimensional space that it covers. The ratio of the perimeter to the area of a shape is simply the perimeter divided by the area. This is easily calculated.

Circle

Step 1

Find the radius of your circle. This is the distance from the center to the outer edge.

Step 2

Calculate the perimeter or circumference of the circle. This can be done using the equation

(C=2pi r)

where r is the radius.

Step 3

Calculate the area of the circle. This can be done using the equation

(text{Area}=pi r^2)

where r is the radius of the circle.

Step 4

Divide the perimeter by the area to obtain the ration of perimeter to area.

Rectangle

Step 1

Find the length and width of the rectangle. This will be the measurement of one of the long sides and one of the short sides.

Step 2

Calculate the perimeter using the formula

(2(b+w)=P)

where b is the base and w is the width.

Step 3

Calculate the area using the formula

(A=bw)

where b is the base and w is the width.

Step 4

Divide the perimeter by the area to obtain the ration of the perimeter to the area.

TL;DR (Too Long; Didn’t Read)

There are an infinite variety of shapes. If you don’t know the formulas for a shape, get creative and try breaking it down into smaller rectangles.