Question

plz help this question

Answer 1

resistance is given by
R = (resistivity x length)/ area of cross section


$r = \beta \times \frac{l}{a} \\ \beta \: is \: the \: resistivity$
$resistance1 = \beta \times \frac{l}{\pi \: \times {r1}^{2} }$
Now r2 = r1 /2
$resistance2 = \beta \times \frac{l}{\pi \times 4 \times {r1}^{2} }$
Taking ratio you will get

$resistance1 = 4 \times resistance2$