Question

A rectangular plate has a length of 21.3

Answer 1

$a=(21.3±0.2)~cm,$

$b=(9.8±0.1)~cm,$

$A=ab=21.3\cdot 9.8±21.3\cdot 0.1±9.8\cdot 0.2+0.2\cdot 0.1=(208.76±4.09)~cm^2.$