From the circular disc of radius 4R two small disc of radius R are cut off. The centre of mass of the new structure will be:

If mass of removed disc is m then mass of big disc will be 16 m.xcm = 16m(0)-m(0)-m(3R)16m-m-m = -314RBecause of symmetry we can say ycm will also have same magnitudeycm = -314Rr→cm = -314R(i^+j^)