the radius is the length of a straight line from the center of the circle to the edge of the circle

theres 3 ways to know the radius and you need to know either the diameter, circumference or area.

diameter
if you know the diameter, all you have to do is half it and that will be your radius.

circumference
if you know the circumference, you need to do the circumference divided by pi times 2

area
if you know the area, you do the square root of the area divided by pi

i hope this guide helped you find the radius, please give me awards so i can feed my starving family thanks ok bye