No:24 tolong pake jalannya ya:)

[tex] \frac{1}{2} \times \pi \times r \times r \\ = \frac{1}{2} \times 3.14 \times 6 \times 6 \\ = \frac{1}{2} \times 113.04 \\ = 56.52 \: [/tex]
Jadi jawabanya (D.) 56,52 cm