A man divided his journey into three parts of distances of 18 km, 20 km and 27 km. He travelled the distances at the speeds of 6 km/h, 5 km/h and 9 km/h, respectively. What was his average speed during the entire journey?
1
7.5 km/h
2
5.5 km/h
3
6.5 km/h
4
4.5 km/h