What is the distance on the ground between two places that are 4cm apart on the street map of Durban

I'm sorry, but to calculate the distance between two points on a map, you will need to know the scale of that map. The scale will tell you how much distance on the ground is represented by a certain distance on the map. Once you have that information, you can use it to calculate the actual distance between the two places. Without knowing the scale, I cannot accurately answer your question.