Let N be the greatest number that will divide 1305, 4665 and 6905, leaving the same remainder in each case. Then the sum of digits of N is:
4
N = H.C.F. of (4665 - 1305), (6905 - 4665) and (6905 - 1305)
= H.C.F. of 3360, 2240 and 5600 = 1120.
Sum of digits in N = (1 + 1 + 2 + 0) = 4.