Calculate the area of the shaded region between two concentric circles, given the inner radius is 2.5 cm and the width of the shaded region is 1 cm.

The radius of the inner circle is given as $r_1 = 2.5 \text{ cm}$.
The width of the shaded region is $1 \text{ cm}$.
The radius of the outer circle is the sum of the inner radius and the width of the shaded region.

$$r_2 = r_1 + 1 \text{ cm} = 2.5 \text{ cm} + 1 \text{ cm} = 3.5 \text{ cm}$$

The formula for the area of a circle is $A = \pi r^2$.

$$A_1 = \pi r_1^2 = \pi (2.5 \text{ cm})^2 = 6.25\pi \text{ cm}^2$$

The area of the shaded part is the difference between the area of the outer circle and the area of the inner circle.

$$A_{\text{shaded}} = A_2 - A_1$$ $$A_{\text{shaded}} = 12.25\pi \text{ cm}^2 - 6.25\pi \text{ cm}^2$$ $$A_{\text{shaded}} = (12.25 - 6.25)\pi \text{ cm}^2$$ $$A_{\text{shaded}} = 6\pi \text{ cm}^2$$

The area of the shaded part is $6\pi \text{ cm}^2$.