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Uncertainty as a percentage is just relative uncertainty multiplied by 100. The percent uncertainty likewise lacks units since it is a ratio of comparable values.

Given Data:

Consider the given data as below.

Blood pressure is measured to be $\mathrm{A}=120Â\pm 2\mathrm{mm}\mathrm{Hg}$.

The uncertainty of blood pressure is $\mathrm{δ}\mathrm{A}=2\mathrm{mm}\mathrm{Hg}$.

The percentage uncertainty is defined by,

$$\begin{gathered} \mathrm{Percent}\mathrm{Uncertainty}=\frac{\mathrm{δ´¡}}{\mathrm{A}}×100\% \\ =\frac{2\mathrm{mm}\mathrm{Hg}}{120\mathrm{mm}\mathrm{Hg}}×100\% \\ =1.67\% \\ :2.00\% \end{gathered}$$

Hence, the measured blood pressure has a percent uncertainty of 2.00%.

The percent uncertainty in measured blood pressure of 80 mm Hg.

The uncertainty in the blood pressure can be calculated as follows:

$\mathrm{Percent}\mathrm{Uncertainty}=\frac{\mathrm{δ´¡}}{\mathrm{A}}×100\%$

Substitute known values in the above equation.

$$\begin{gathered} 1.67\%=\frac{\mathrm{δ´¡}}{80\mathrm{mm}\mathrm{Hg}}×100\% \\ \mathrm{δ´¡}=\frac{1.67×80}{100} \\ =1.336 \\ :1\mathrm{mm}\mathrm{Hg} \end{gathered}$$

Hence, the uncertainty in blood pressure is1 mm Hg.