The average speed of the boat is 9.1 km/hr. The ratio between the speed of the stream and the upstream speed of the boat is 3: 7. The sum of the time taken by the boat to travel (D + 23) km downstream and (1.2D - 27) km upstream is 60 hours. Find the time taken by the boat to cover D km in still water
1
32 hours
2
25 hours
3
20 hours
4
16 hours
5
36 hours