radius 2 cm has its area = 4pi square cm while radius 4 cm has the area = 16 pi square cm...
No,it is not necessary. But, the area becomes four times the area of the previous circle. For example, let the radius of a circle be 5 cm. area= 25pi square cm. if radius is doubled,i.e., radius becomes 10 , then, area=100pi square cm.
