If you alternate the direction of the sections of the circle, you create a parallelogram with a base equal to half of the circumference of the circle and a height equal to the radius of the circle.
b = (1/2) (circumference of circle) = (1/2) (2π r) = π r
h = r
A = 42.25 π cm2 = b*h = (π r) * (r) = π r2
→ r = √42.25 = 6.5 cm
h = r = 6.5 cm