Answer
$14.69\ (\Omega)$
Work Step by Step
Step 1. Let the resistance be $R$, the length of the conductor be $L$, the radius of the conductor be $r$, we have $R=\frac{kL}{r^2}$ where $k$ is a constant.
Step 2. Use the given conditions, we have $10=\frac{50k}{(6\times10^{-3})^2}$, thus $k=1.2\times10^{-6}$
Step 3. For $L=100, r=7\times10^{-3}$, we have $R=\frac{1.2\times10^{-6}\times100}{(7\times10^{-3})^2}\approx14.69\ (\Omega)$
