Question

If the area of a circle is 16pi what is the circumference of the circle, circle b, if its radius is 1/2 that of the circle a

Answer 1

First find the radius of circle A. You know that the equation is r^2*pi, so just divide both by pi.
r^2*pi=16pi
/pi          /pi
r^2=16
R is 4. That means that circle B is 2, since its radius is half that of circle A.
C=pi2r
C=pi2(2)
C=pi4
C=4pi
The answer is 4pi.