keliling daerah yang di arsir

1/2x22/7x42=66
1/2x22/7x42=66
1/2x22/7x21=33
66+(66-33)
=99
maaf kalo salah

r1= r2=1/2 *42= 21 cm
r3= 1/2 *21= 21/2

k1=k2= 1/2 *2*π*r1= 22/7 *21= 66 cm
k3= 1/2 *2*π*r3= 22/7 * 21/2= 33 cm

keliling= k1+k2+k3+42+42-21
keliing= 66+66+33+42+21
keliling= 132+96
keliling= 228 cm