A person takes a contract to construct a road. He constructs 20% of the road on the first day, 30% of the remaining road on the second day, 50% of the remaining road on the third day, and the remaining 7 km of the road on the fourth day. What is the total length of the road?

In a town with 30,000 professionals, teachers make up 11% of the total professionals. If 46% of teachers are male, what is the number of female teachers in the town?

In a town's professional breakdown, doctors represent 18% and clerks represent 8% of the total professionals. If the number of doctors is 3000 greater than the number of clerks, what is the total number of professionals in the town?