Answer:
use the percentage error relation
Step-by-step explanation:
The percentage error in anything is computed from ...
%error = ((measured value)/(accurate value) -1) × 100%
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The difficulty with voltage measurements is that the "accurate value" may be hard to determine. It can be computed from the nominal values of circuit components, but there is no guarantee that the components actually have those values.
Likewise, the measuring device may have errors. It may or may not be calibrated against some standard, but even measurement standards have some range of possible error.