If a lead can be extrated with 92.5% efficiency, what is the mass of ore required to make a lead sphere with 750%cm radius

The mass of ore required is 21 700 t.

r = 750 cm

V = = = 1.767 × 10⁹ cm³

The density of lead is 11.34 g/cm³.

So mass of lead sphere = 1.767 × 10⁹ cm³ × = 2.004 ×10¹⁰ g

2.004 ×10¹⁰ g × = 2.004 × 10⁷ kg

2.004 × 10⁷ kg × = 2.004 × 10⁴ t

92.5% efficiency means 92.5 t Pb per 100 t of ore.

Mass of ore = 2.004 × 10⁴ t Pb × = 2.17 × 10⁴ t ore = 21 700 t ore