Question 1 of 4

A circular disc of radius r has uniform thichness.  A circular hole of diameter equal to the radius of the disc has been cut out as shown.  The centre of gravity of the remaining disc lies on the diameter of the disc at a distance x to the left of the centre of the original disc.  The value of x is

(1) r                              (2) r2

(3) r4                           (4) r6