please solve this question

Given l₁ = 1m.

l₂ = 2m.

 

As the mass of the wire will remain constant and it is given that density remains constant that mean volume is also constant, therefore

 

l₁xA₁ = l₂xA₂

 

i.e., A₂ = l₁xA_1/l_{2 =} A_1/2

 

Now we have, R₁ = rxl₁/A_{1                  where r = resistivity of the wire}

 

and R₂ = rxl₂/A₂

           = rx(2l₁/(A_1/2))

           = 4x(rxl₁/A1)

           = 4R₁