Refrain from using centimeters

I will light red when I have an example of what I think is not a good idea. I will highlight good usages of the SI in light yellow.
What is the area, and its approximate uncertainty, of a circle of radius
3.1×
4
10
cm
?
Instead, use meters or millimeters squared for area.
What is the area, and its approximate uncertainty, of a circle of radius 310 m?
What is the area, and its approximate uncertainty, of a circle of radius 310 m?
What is the area, and its approximate uncertainty, of a circle of radius 310 000 mm?
In[]:=
radius=
(310.±10.)
m
;
In[]:=
area=
2
radius
π
Out[]=
(3.02±0.19)×
5
10
2
m
To express the area of the circle write something like:
(3.02±0.19)×
5
10
2
m
(3.02±0.19)×
11
10
2
mm
(0.302±0.019)
2
km
Don’t write:
(3.02±0.19)×
9
10
2
cm