Answer:
8. 272 m²
10. 306.9 km²
12. 311.4 m²
Step-by-step explanation:
8. the surface area =
(10×10)+(4×½×10× 8.6)
= 100 + 172 = 272 m²
10. the surface area =
(11×7)+(2×½×7×13.2)+(2×½×11×12.5)
= 77+92.4+137.5= 306.9 km²
12. the surface area =
(9×9) +(4×½×9×12.8)
= 81+230.4 = 311.4 m²
