tolong dibantu yah pake cara.

Diketahui =
r = 21 cm
sudut pusat(a) = 120°

Panjang busur = a . 2πr
Panjang busur = 120/360 . 2 . 22/7 . 21

= 1/3 . 2 . 22 . 3
= 2 . 22
= 44 cm (C)