Resistance of a wire is R and cross-section area is A now areas change to N times.
We need to find new resistance.
We know that
Resistance,R = ρl/A
ρ=Resistivity of the wire
l=lenght of wire
A= cross-section of the wire
When we increase the length of wire by n times
Let us assume the initial and final radius of the wire be r1,&r2 respectively.
Irrespective of increase in length the volume remains the same
Since the initial and final volume are equal
2π(r1^2)l = 2π(r2^2)(nl)
So, the cross-sectional area becomes 1/n times the initial value.
Substituting the values in the formula for resistance, we get
new resistance n2 times greater than the initial value of resistance.