The correct question is:

Three solid metallic spherical balls of radii 3 cm, 4 cm and 5 cm are melted into a single spherical ball. What will be its radius?

Solution:

Let r₁ , r₂ ,r₃ are the radii of the given 3 spheres.

So, r₁ = 3, r₂ = 4, r₃ = 5

Again, let radius of the new sphere is R

Now, given Three solid metallic spherical balls are melted into a single spherical ball.

So, sum of volume of the three sphere = volume of the new sphere

=> (4/3)*π*r₁³ + (4/3)*π*r₂³ + (4/3)*π*r₃³ = (4/3)*π*R³

=> r₁³ + r₂³ + r₃³ = R³

=> 3³ + 4³ + 5³ = R³

=> R³ = 27 + 64 + 125

=> R³ = 216

=> R = ³√216

=> R = ³√(6*6*6)

=> R = 6

So, the radius of the new sphere is 6 cm.