The perimeter of the figure is 82.275cm.
In order to find this, we must first find the length of the arc portion. For this we will use circumference of a circle formula and then cut the amount in half (since it is a semi circle). The formula is below:
2[tex]\pi[/tex]r = C
We know the radius is 9 since it is half of the 18 that is the full diameter.
2[tex]\pi[/tex](9) = C
28.275 = C
Now we add that to the 3 other sides, which are all 18.
28.275 + 18 + 18 + 18 = 82.275
