Rohan is 9 times faster than Sohan
So when Sohan completes one round, Rohan completes 9 rounds
i.e. Rohan has been diametrically opposite to Sohan 9 times as in each round of Rohan, diametrically opposite position is possible only 1 time.
now when Sohan completes 3 such rounds...
desired answer = 9*3 = 27