The formula for Young's modulus is given by
Y==lΔlAFAΔlFl
From above equation, it follows that
Δl=AYFl...(1)
Again, volume of the wire is given by
V=Al⇒l=AV
Hence, from equation (1),
Δl=A2YFV...(2)
As, Y and V is the same for both the wires,
Δl∝A2F
Hence, for two wires, it can be written that
Δl2Δl1=A12F1×F2A22...(3)
As Δl1=Δl2, from equation (3), it follows that
F1A22=F2A12⇒F2F1=A22A12=(14)2=16