Răspuns:
Explicație pas cu pas:
ducem CE⊥AB DF⊥AB
AF=EB=(AB-CD)/2=(12-8)/2=4/2=2m
cos 60°=EB/BC=1/2 2/BC=1/2 BC=4 m
CE=BCsin60=4√3/2=2√3 cm
A=(AB+CD)·CE/2=(12+8)·2√3/2=20√3 m²
1m²......................................0,1 kg
20√3 m²...........................x=2√3m²≅3,46 kg