
Answer:
d(A) = 8 cm²
Step-by-step explanation:
Area of a rectangle is:
A(r) = L * w
L is the length, and w is the width, then
d(A) = L* dw + w*dl  Â
From problem statement we know:
L = 42 cm     w = 38 cm
With an error in measurement of 0,1 cm in each case, then
dw = dl = 0,1 cm
And
d(A) = 42*0,1 + 38*0,1   ⇒  d(A) =  4.2 + 3.8   ⇒   d(A) = 8 cm²