A solid metallic sphere of radius 9 cm is melted and recast into a wire of radius 2 cm. What is the length of the wire?

Let's assume the length of the wire is 'y' cm.

A solid metallic sphere of radius 9 cm is melted and recast into a wire of radius 2 cm. 

Volume of sphere = Volume of wire

$$\frac{4}{3}\times\ \pi\ \times\ \left(radius\ of\ sphere\right)^3=\pi\ \times\ \left(radius\ of\ wire\right)^2\times y$$

$$\frac{4}{3}\times\ \pi\ \times\ \left(9\right)^3=\pi\ \times\ \left(2\right)^2\times y$$

length of the wire = y = 243 cm