Percent difference and uncertainty

[mike2601]

Homework Statement

How do we solve this problem?
% Difference = (l 0.282 +/- 0.0019 - 0.288 +/- 0.04 l) / 0.285 +/- 0.02

Homework Equations

Percent Difference = (l value - average value l) / average value x 100%

The Attempt at a Solution

many attempts made but cannot get correct uncertainty for the answer

 

[Delphi51]

Welcome to PF, Mike.
You are supposed to show your attempt(s) so we have some idea what method you are supposed to use, and to avoid giving solutions to people who haven't tried the problem on their own.

For the subtraction, I would add the uncertainties.
For the division, I would convert the uncertainties into per cents of the main values, add the per cents, and finally find that % of the main value.