An iron ball of radius 21 cm is melted and recast into spherical balls of radius 7 cm. Find the number of spherical balls.

Correct option is D

Given:
Radius of the large iron ball = 21 cm
Radius of the small spherical balls = 7 cm
FormulaUsed:
Volume of a sphere = $$\frac43$$​πr³.
Solution:
=> Volume of the large iron ball = $$\frac 43$$​π × (21)³
=> Volume of a small spherical ball = $$\frac 43$$​π × (7)³
Number of small balls = $$\frac{\text{Volume of the large ball}}{\text{Volume of a small ball}} = \left(\frac{21}{7}\right)^3 = 27$$​​