A 50 cm3 block of metal is made into wire of diameter 1 mm. How long will the wire be?

1 mm  =  .1 cm

So  the radius  of  the wire  =  .1 cm / 2  =  .05cm

The  cross-section  of the  wire  =  pi *(.05)cm^2   =  [.0025 pi]cm^2

The  volume of the wire  =  Cross-Section * Length  =  The volume of the block of metal

So  we  have this

50cm^3   =  [ .0025]cm^2  *  length

50 / .0025   = length   =   20,000cm