The perimeter of the composite shape is: (3π + 12)mm
<h3>What is a semicircle?</h3>
A semicircle is a part of a circle cut through its diameter.
Analysis:
perimeter of a semicircle = πr
where r = 6/2 = 3mm
perimeter of a semicircle = π(3) = 3π
perimeter of incomplete rectangle = L+2B, L = 6mm, B = 3mm
perimeter of rectangle = 6mm +2 x 3= 12mm
perimeter of shape = (3π+12)mm
In conclusion, the perimeter of the rectangle is (3π+12)mm
Learn more about semicircles :brainly.com/question/285710
#SPJ1