The area of a trapezium = ½(a + b)h
Where
a = top length
b = bottom length
h = height
∴ Area of trapezium
= ½(8 + 12)(6)
= 60cm²
The volume of prism
= base area × length
= 60 × 20
= 1200cm³
Density = 5g/cm³
Mass = Density × Volume
Mass = 5g/cm³ × 1200cm³
Mass = 6000g
Convert g to kg = 6000g ÷ 1000 = 6kg
Mass of the prism = 6kg