What is the area of a circle

To calculate the area of a circle, we have this formula:

Let's do an example: Calculate the are of a circle whose diameter is 20 cm.

First, we need to get the radius of the circle. WWe should know the diameter of a circle is equal to , so the radius is half of the diameter.

If the diameter is 20 cm, then the radius is 10 cm.

Now we have the radius and teh formula , so we can calculate:

= 314.16

what does x eaqual

step-by-step explanation:

a 4/6 = 9/12   not proportional

step-by-step explanation:

to find which are not proportional, we can use cross products

if it is true, they are proportional.   if it is not true, they are not proportional.

a 4/6 = 9/12

4* 12 = 6*9

48 = 54

not this is not proportional  

b 2/3 = 12/18  

2* 18 = 3 * 12

36 = 36

this is proportional

c 5/4 = 10/8  

5*8 = 4*10

40 = 40

this is proportional

d 7/5 = 35/25

7*25 = 5 * 35

175 = 175

is proportional