Part 1
We need to find the perimeter of a circle with a diameter of 18 inches.
The relation between the perimeter P and the diameter d is given by:
[tex]P=\pi d[/tex]
Since d = 18 inches and we need to use 3 for π, we obtain:
[tex]P=3\cdot18\text{ inches }=54\text{ inches}[/tex]
Therefore, the ribbon needs to be 54 inches long.
Part 2
We need to find the perimeter of a semicircle with a radius of 8 in.
The perimeter of this semicircle is the sum of half the perimeter of the whole circle and the line segment formed by two radii.
The relation between the perimeter P and the radius r of a circle is:
[tex]P=2\pi r[/tex]
Thus, half the perimeter is:
[tex]\frac{P}{2}=\pi r[/tex]
Since we need to use 3 for π and r = 8 in, we obtain:
[tex]\frac{P}{2}=3\cdot8\text{ in }=24\text{ in}[/tex]
And the line segment measures:
[tex]2\cdot8\text{ in }=16\text{ in}[/tex]
Therefore, the perimeter of the calzone is:
[tex]24\text{ in }+16\text{ in }=40\text{ in}[/tex]
Answer: 40 in.
