The product of two inches and the circumference of a circle, in inches, is equal to the circle’s area. What is the length of the radius of the circle, in inches?
2 * ( 2*pi * r) = pi * r^2 divide through by pi
2 * 2 * r = r^2
4 r = r^2 rearrange as
r^2 - 4r = 0 factor
r ( r - 4) = 0
Set each factor to 0 and solve for r and we get that
r = 0 inches (reject)
r = 4 inches (accept)
