tolong jelaskan caranya kak

K ½ lingkaran
=½ ×2 ×π ×r
=½ × 2 × 22/7 × 21/2
=11 × 3
=33

K = 33×2
K = 66 + 21
K =87cm

Keliling daerah yang diarsir
= 2 (keliling 1/4 lingkaran) + keliling 1/2 lingkaran + 2 (1/2 x 21)
= keliling 1/2 lingkaran + keliling 1/2 lingkaran + 2 (21/2)
= keliling 1 lingkaran + 21 cm
= (π x d) + 21 cm
= (22/7 x 21 cm) + 21 cm
= 66 cm + 21 cm
= 87 cm

Jawabannya D