Answer:
1 cm : 800 km or 1/80,000,000
Explanation:
A model or map scale is often expressed as ...
(1 unit of A on the model) : (N units of B in the real world)
We're given the relative measurements as ...
15 cm : 12,000 km
Dividing by 15 gives the unit ratio as above:
1 cm : 800 km
__
A scale can also be expressed as a unitless fraction. To find that, we need to convert the units of both parts of this ratio to the same unit.
0.01 m : 800,000 m
Multiplying by 100, we get ...
1 m : 80,000,000 m
Since the units are the same, they aren't needed, and we can write the scale factor as ...
1 : 80,000,000 or 1/80,000,000