Tolong dijawab no. 20-21 pake cara ya... Makasih.

21. diketahui = D =28 cm
r = 28:2=14
t = 48 cm
jawab = 1/3 × 22/7 × 14 × 14 × 48
= 1 × 22 × 2 × 14 × 16
= 9856

21.Dik :
[tex]d \: = 28 \\ d = \frac{1}{2} \times 28 = 14cm \\t \: = 48cm [/tex]
Dit : luas?
Jwb :
[tex] \frac{1}{3} \times \frac{22}{7} \times 14 \times 14 \times 48 \\ \frac{1}{3} \times 22 \times 2 \times 672 \\ 224 \times 22 \times 2 \\ \frac{9856}{2} = 4928[/tex]
Kok gak ada isiannya ya? Atau mungkin saya yg salah isi,,