A load of 2kg produces an extension of 1mm in a wire of 3m in length and 1mm in diameter. Find Young's modulus of wire.

F=2*10=20N
L=3m
L'=1/1000m
Area=pi*(r)^2
Take r=(1/2000)^2 because diameter is given so convert it into radius, also you have take it in 'm'.
So,Y=F*L/A*L'
=20*3*2000*2000*1000/3.14
=76433121000
=7.64*10^10N/m^2