Hey, for this kind of question, I would reccomend you to do it
step by step, there's no hurry during the exams. (:
So, given that,
4cm : 8000m
=> 4 cm : 800 000 cm
For area, since the units are cm^2 and km^2 respectively, it
means simply (cm * cm) and (km * km), just like a * a = a^2, with
this understanding we'll change the units respectively to what the
question requires:
4 cm : 8 km
If we square our units, we have to square our numbers as well,
so we'll have:
4^2 cm^2 : 8^2 km^2
16 cm^2 : 64 km^2
By simple proportion,
64 km^2 -> 16 cm^2
4 km^2 -> 16/64 * 4
= 1
cm^2
(: I hope I don't make any mistakes, but it should be
correct.