How can you find the radius of a circle if you know the area?

Answer 1

Formula for the area of a circle:

A = pi * r^2

where A is the area and pi is the number 3.141592654....

re-arrange the formula:

r = SQRT (A/pi)

where SQRT is the square root function.

Answer 2

The formula to find the area of a circle = pi x radius^2

pi x radius^2 = area
radius^2 = area/pi
radius = square root of (area/pi)

Answer 3

The square root of ( 7times the area of the circle divided by 22).
We assume here pi to be equal to 22/7 and area of a circle equals pi times the square of the radius.

Answer 4

The area of a circle is pi*r^2
then if u have the area
divide it by pi
you will get the radius squared
then find the square root of the number you get
you will get the radius
i hope this helped

Answer 5

the area of a circle equals pi times the radius^2

A=(pi)r^2

so substitute the area for (A) in the equation, divide by pi and you'll have the radius squared. Find the square root of the number you have and you'll have the radius

Answer 6

Area = Pi * radius * radius = Pi * radius^2

radius ^ 2 = Area / Pi
radius = square root ( area / Pi )

Answer 7

Because the area of a circle is pi x r^2 where r is the radius, the radius of the circle if you know the area is sqrt(A/pi).

I know this isn't said very clear, so if you want to see the information clearer, go to http://www.artofproblemsolving.com/LaTeX/AoPS_L_TeXer.php
For pi x r^2, enter in "\pi \cdot r^2" without the quotes (the dot is multiply) and for sqrt(A/pi), enter in "\sqrt{\frac{A}{\pi}}" also without the quotes.

Answer 8

if the area is A the radius is R and we know that A=pi times R then R=sqrt A/pi

Answer 9

Area=pi * radius squared
A/pi=r^2
square root of (A/pi)=r

or if the area is given in terms of pi, like 25pi, just take the square root of the coefficient (25) to get your radius (5)

Answer 10

since the area of a circle is: r^2*3.14
then divide the area by 3.14 and you'll get r^2 and if you find the square root of that, it will be the radius.