Given,

Radius of the spherical ball = 3 cm

After recasting the ball into three spherical balls;

Radius of the first ball = r₁ = 1.5 cm

Radius of the first ball = r₂ = 2 cm

Let the radius of the third ball be r₃ cm.

Then,

Volume of third ball = Volume of spherical ball – volume of 2 small balls

Volume of the third ball = π × 3³ – π – π × 2³

36π – – 32π/3cm³ = 125π/6cm³

4/3πr³ = 125π/6

r³ = 125π × 3/6 × 4 × π = 125/8

r = = 2.5 cm

Hence, the radius of the third ball is 2.5cm.