A cylindrical wire has a resistance of R and resistivity p D

A cylindrical wire has a resistance of R and resistivity p. Determine its resistivity in terms of p if its length and diameter are both doubled.

The resistivity of a material is constant. Changing the length and diameter affect the resistance, but not the resistivity. R=pl/A where R is the resistance, p is the resistivity , l is the length, and A is the cross-sectional area.