tolong bantuin ya, no. 6,,a-e,,,, pakai caranya,,,, terimakasih

[tex]a. \: l = \pi {r}^{2} = \frac{22}{7} \times (2.8)^{2} = 22 \times 0.4 \times 2.8 = 24.64 \\ b. \: l = \pi {r}^{2} = \frac{22}{7} \times (14)^{2} = 22 \times 2 \times 14 = 616 \\ c. \: l = \pi {r}^{2} = \frac{22}{7} \times (21)^{2} = 22 \times 3 \times 21 = 1386 \\ d. \: l = \pi {r}^{2} = \frac{22}{7} \times (35)^{2} = 22 \times 5 \times 35 = 3850 \\ e. \: l = \pi {r}^{2} = \frac{22}{7} \times (40)^{2} = 22 \times 5.7 \times 40 = 5016[/tex]