The shaded portion area A corresponds to the area Ao of the outer circle minus the area Ai of the inner circle:
A = Ao - Ai
Also, the area of each circle of radius r is given by:
π r²
where the radius r is half the diameter d.
So, using r = d/2 in the above formula, we obtain:
π r² = π (d/2)² = (π/4) d²
Now, replacing each area with the corresponding diameter, we find:
A = Ao - Ai
= (π/4) 4² - (π/4) 1.5²
= (π/4) (4² - 1.5²)
= (π/4) (16 - 2.25)
= (π/4) (13.75)
≅ 10.799
Rounding the result to one decimal place, we find the answer:
10.8 m²