A cylindrical vessel with radius 6 cm and height 5 cm is to be made by melting a number of spherical metal balls of diameter 2 cm. The minimum number of balls needed is:

A. 125

B. 135

C. 115

D. 105

Answer: Option B

Solution(By Examveda Team)

$$\eqalign{ & \pi {r^2}h = \frac{4}{3}\pi {R^3} \times n \cr & {6^2} \times 5 = \frac{4}{3} \times {1^3} \times n \cr & n = 135 \cr} $$