Suppose that you have a circle with a radius of 4.02 ± 0.39 m, what is the calculated uncertainty in the area?
The range of uncertainty will be from
pi*(4.41)^2 to pi*(3.63)^2.
Write that in +- form.
The middle of that range will not quite be
pi*4.02^2. It is pi*4.039^2 = 51.25 m^2
The lower limit is 41.40 m^2. The upper limit is 61.10 m^2
A = 51.25 +/- 9.85 m^2