we have to calculate the perimeter of the semicircle which radius is 16 mm
[tex]P_{sc}=\frac{2\pi\cdot r}{2}=\pi\cdot r=16\pi\approx50.26\operatorname{mm}[/tex]Now we have to add the outter sides of the triangle
[tex]P=20+20+50.26=90.26\operatorname{mm}[/tex]