Given ${\mathrm{\lambda }°}_{{\mathrm{Mg}}^{2+}}=106 \mathrm{S}{ \mathrm{cm}}^2{ \mathrm{mole}}^{-1}, {\mathrm{\lambda }°}_{{\mathrm{SO}}_4^{2-}}=160 \mathrm{S}{ \mathrm{cm}}^2{ \mathrm{mole}}^{-1}.$ The value of ${\mathrm{\lambda }°}_{{\mathrm{MgSO}}_4}$ (in $\mathrm{S} {\mathrm{cm}}^2 {\mathrm{mole}}^{-1}$)  is

This question is based on kohlrauschs law, according to this law, at infinite dilution, when electrolyte is complete dissociated then each ion makes a definite contribution towards molar conductivity of the electrolyte irrespective of the nature of the other ion with which it is associated. 

$$\begin{gathered} {\mathrm{\lambda }}^0\left[{\mathrm{MgSO}}_4\right] = {\mathrm{\lambda }}^0\left[{\mathrm{Mg}}^{+2}\right]+ \left[{{\mathrm{SO}}_4}^{-2}\right] \\ {\mathrm{\lambda }}^0\left[{\mathrm{MgSO}}_4\right] =[106 \mathrm{S} {\mathrm{cm}}^2{\mathrm{mole}}^{-1}] +[106 \mathrm{S} {\mathrm{cm}}^2{\mathrm{mole}}^{-1}] \\ {\mathrm{\lambda }}^0\left[{\mathrm{MgSO}}_4\right] =212 {\mathrm{cm}}^2{\mathrm{mole}}^{-1} \end{gathered}$$