Solution:

Given radius of each sphere, r = 2 cm

Volume of a sphere = (4/3)r³

= (4/3)×2³

= (4/3)×8

= (32/3) cm³

Volume of 8 spheres = 8×(32/3)

= (256/3) cm³

Let R be radius of new sphere.

Volume of the new sphere = (4/3)R³

Since 8 spheres are melted and casted into a single sphere, volume remains same.

(4/3)R³ = (256/3)

4R³ = 256

R³ = 256/4 = 64

Taking cube root

R = 4 cm

Hence the radius of the new sphere is 4 cm.