Hi
Let speed of man be v
Now in downstream effective speed = v+4.5
Now as per given condition : (45/v+4.5) =2 so v+4.5=22.5 so we get v=18
Now distance required to cover in upstream = 45 (1.5)=67.5
Now therefore time = (67.5/v-4.5) (In upstream effective speed is speed of man - speed of current )
solving we get 67/13.5
so time = 5 hours.