A cylindrical conductor of length l  uniform area of cross-section A has resistance R. What should be the area of cross-section of another conductor of same material to have the same resistance.

Dear Student,
Resistance of a conductor,
 $$\begin{gathered} R=\rho \frac{l}{A} \\ where, \\ \rho is the resistivity of the material \\ l = length of the conductor \\ A = area of cross-section of the material \end{gathered}$$

For another conductor of same material to have the same resistance, the area of cross-section can be determined in terms of its length.
Let the length of the conductor be l' and its area of cross-section be A', then
$$\begin{gathered} \rho \frac{l\text{'}}{A\text{'}}=R \\ \rho \frac{l\text{'}}{A\text{'}}=\rho \frac{l}{A} \\ \frac{l\text{'}}{A\text{'}}=\frac{l}{A} \\ A\text{'}=\frac{A}{l}l\text{'} \end{gathered}$$

Regards