These are my measurements: D1 = 5.381 +/- 0.001 cm D2 = 2.070 +/- 0.001 cm t = 0.304 +/- 0.005 cm m = 40.04 +/- 0.005 g I then calculated the uncertainties of D1 and D2 squared: D1^2 = 28.95 +/- 0.01 cm^2 D2^2 = 4.285 +/- 0.004 cm^2 D1^2 - D2^2 = 24.67 +/- 0.01 cm^2 Up until there, I'm pretty sure everything is correct. Than I had to calculate the volume of the washer by using the equation: (pi x (D1^2 - D2^2) x t)/4 And I basically got stuck there. I'm not sure how to calculate my uncertainties when multiplying by t and so on. I tried it out by first adding the uncertainties of Dtotal and t (when multiplied) by using this equation: Dtotal^2 x t +/- Dtotal^2 x t x (change in Dtotal/Dtotal + change in t/t) That gave me a volume of 5.9 +/- 0.1 cm^3... which I then used to calculate a density of 6.8 +/- 0.1 g/cm^3. Does this seem correct or what am I doing wrong? I also don't know how to express my answers while doing the calculations; as in, I have random numbers from subtracting my givens (while subtracting my uncertainties) that I don't end up using. I'm really confused.