Step-by-step explanation:
w = (4.52 ± 0.02) cm, x = ( 2.0 ± 0.2) cm, y = (3.0 ± 0.6) cm. Find z = x + y - w and its uncertainty.
z = x + y - w = 2.0 + 3.0 - 4.5 = 0.5 cm
Dz = Dx + Dy + Dw = 0.2 + 0.6 + 0.02 = 0.82 rounding to 0.8 cm
So z = (0.5 ± 0.8) cm
Solution with standard deviations, Eq. 1b, Dz = 0.633 cm
z = (0.5 ± 0.6) cm
Notice that we round the uncertainty to one significant figure and round the answer to match.