A shot-put iron sphere of diameter 2 cm is melted and cast into a solid cylinder of height 2 cm. What will be the diameter of the cylinder thus made?

Sphere radius = $6$ cm

Sphere volume:

$V = \frac{4}{3}\pi r^3$

$= \frac{4}{3}\pi (6)^3$

$= 288\pi$

Cylinder height = $2$ cm

Let cylinder radius = $R$

Cylinder volume:

$V = \pi R^2 h$

$= \pi R^2 \times 2$

$= 2\pi R^2$

Since volume remains same:

$2\pi R^2 = 288\pi$

$R^2 = 144$

$R = 12$

Diameter of cylinder = $2 \times 12 = 24$ cm

Correct answer: 24 cm