Answer:9R or R'=9pL1/A1 or the resistance has increased 9 times the original resistance
Step-by-step explanation:
When we then to enlongate a wire such that the area of the wire diminshes so As to have a constant volume.
From the relation
R=pL1/A1
Where p=resistivity
L1=original length
R=resistance
A1=original area
L2=3L1.since the volume remain constant
A1L1=A2L2
A2=A1L1/3L1
A2=A1/3
Since the resistance and resistivity of the wire does not change before strecting and after stretching
L1= 3L1
A2=(A1/3)
R'=pL2/A2
R'=p 3L1/ (A1/3)
R'=p9L1/A1
R'=9pL1/A1
R=pL1/A1
So the resistance has increased 9 times the original resistance