The diameter of a metallic ball is 4.2 cm. What is the mass of the ball, if the density of the metal is 8.9 g per cm³?

Radius of metallic ball r = 4.2/2 = 2.1 cm
Therefore, the volume of metallic ball = 4/3πr³
= 4/3 × 22/7 × 2.1 × 2.1 × 2.1
= 4 × 22 × 0.1 × 2.1 × 2.1
= 38.808 cm²
Here, the mass of 1 cm³ = 8.9 × 38.808 = 345.39g(approx)
Hence, the mass of the ball is 345. 39 gram.