The scale of a map is given as 1:2,0000. Two cities are 3 cm apart on the map. Calculate the actual distance between them.

1 cm on map = 20000 cm for real

3 cm on map = 60000 cm for real

60000 cm = 600 m = .6 km

(you might have a typo, I believe in the US, a comma may be inserted to group large numbers by sets of three's
e.g. $ 21,000,000 for 21 million
you have 4 zeros after the comma.
Adjust my answer accordingly)