Question 60 of 118

Two separate wires $A$ and $B$ are stretched by $2mm$ and $4mm$ respectively, when they are subjected to a force of $2N.$ Assume that both the wires are made up of same material and the radius of wire $B$ is $4$ times that of the radius of wire $A.$ The length of the wires $A$ and $B$ are in the ratio of $a:b.$ Then $\dfrac{a}{b}$ can be expressed as $\dfrac{1}{x}$, where $x$ is _____.