Final answer:
The scale of the map is 1 cm : 0.3 km.
Step-by-step explanation:
To find the scale of the map, we need to determine how many centimeters represent 1.2 kilometers. 
We can set up a proportion to solve for the scale: 4 cm / x = 1.2 km / 1. Cross multiplying gives us 4x = 1.2. 
Dividing both sides by 4, we find that x = 0.3. Therefore, the scale of the map is 1 cm : 0.3 km.