Answer:
radius of semi circle is 16mm.
diameter of semi circle is 32mm.
perimeter of triangle=sum of all sides.
perimeter of triangle = 20mm+20mm+32mm
perimeter of triangle =72mm
perimeter of semi circle=pi×r
perimeter of semicircle = 3.14×16mm
perimeter of semicircle =50.24mm
perimeter of the figure= 72mm+50.24mm=122.24mm