When two or more quantities are multiplied, the error in result (Eproduct) is the square root of the sum of the square of the fractional errors of the individual quantity. Thus,
where EA and EB are errors in observed values of A and B respectively.
For example: A rectangle is measured 160.881 ± 0.026 cm long and 75.007 ± 0.001 cm wide. The error in its area (12,067 cm2) is
