Tolong no 15 ya!!...

L 1/2 lingkaran
[tex] = \frac{1}{2} \times \pi \times {r}^{2} \\ = \frac{1}{2} \times 3.14 \times {10}^{2} \\ = \frac{1}{2} \times 314 \\ = 157 \: {cm}^{2} [/tex]
Jawabannya yg A