A solid sphere has a radius 21 cm. It is melted to form a cube. 20% material is wasted in this process. The cube is melted to form hemisphere. In this process 20% material is wasted. The hemisphere is melted to form two spheres of equal radius. 20% material was also wasted in this process. What is the radius (in cm) of each new sphere?
Show answer & explanation
Correct answer: C
Explanation
The correct answer is option 3, i.e. 8.4(∛4)
AQ
4/3 × π × (21)3 × (4/5)3 = 2 × 4/3 × πr3
r3 = 43/53 × 213/2
r = 2×21/5 × ∛4
r = 8.4∛4 cm