The two semi circles come together to form one circle 
Hence their total perimeter 
C= πd ,d= 4 + 4 = 8 
   = π x 8
   = 25.13 cm 
Considering the perimeter b/n the two semi circles . That figures also form a square when combined perimeter of a square is P= 4L 
With L =4 
P= 4(4) = 16 cm 
Hence the TOTAL Perimeter 
= 16 + 25.13
= 41.13 cm