Geometry circles circutes in mathematics with example

what is the diameter of a circle if its area is 100pi cm^2 ?

solution

First,write the formula,

A=r^2 pi 

now, substitute in what you know.

100 pi=r^2 pi 

by dividing both sides of equation by pi 

100=r^2

then,take the square root of both sides

10=r

Remember that you are solving for diameter 

d=2r

d=2×10

d=20

the answer is the diameter , d= 20

The area of circle is 25 pi . what is the radius?

 first write the formula , A=pi r^2

 substitute in what you know.

25pi = r^2pi

by dividing both sides of the eq. by pi 

25=r^2

take the square root of both sides 

5=r 

the answer is r=5 .