Question

How to calculate percentage error in series resistance?

Answer 1

The methods you were trying is for finding error when the resultant resistance is to the power one. Like in series. But here it is of power -1. So differentiating we get dR/R^2 = dr/(r1)^2 + dr/(r2)^2. This implies: dR = [3/10000 + 4/ 40000] *4444.9. dR=1.78 ohms The answer you required is obtained.