Let the time taken by Ram, Aman, and Chandan alone to finish the work be ‘x’, ‘y’ and ‘z’ days respectively. According to the question ∶ (1/x) + (1/y) = (1/7.2) ----(1) (1/x) + (1/y) + (1/z) = (1/4) ----(2) From (1) and (2) ∶ (1/z) = (1/4) – (1/7.2) (1/z) = (1.8 – 1)/7.2 z = 9 days Hence, time taken by Chandan alone to finish the work = 9 days Thus, the correct answer is option 3.