Equivalent weight of a substance varies with valency. Equivalent weight of potassium permanganate in acidic medium is ‘X’ and in neutral medium is ‘Y’ . X:Y is

Acidic medium:  

                             $$\begin{gathered} \stackrel{+7}{\mathrm{Mn}}{\mathrm{O}}_4^{-}\to {\mathrm{Mn}}^{+2} ; \\ \mathrm{Decrease} \mathrm{in} \mathrm{oxidation} \mathrm{state} \mathrm{per} \mathrm{mole} =5 \\ \mathrm{EW} \left(\mathrm{X}\right) =\frac{\mathrm{M}}{5} \end{gathered}$$

Neutral medium :

                               $$\begin{gathered} \stackrel{+7}{\mathrm{Mn}}{\mathrm{O}}_4^{-}\to \stackrel{+4}{\mathrm{Mn}}{\mathrm{O}}_2 \\ \mathrm{Decrease} \mathrm{in} \mathrm{oxidation} \mathrm{state} \mathrm{per} \mathrm{mole} =3 \\ \mathrm{EW}\left(\mathrm{Y}\right) =\frac{\mathrm{M}}{3} \end{gathered}$$

$\therefore$ X : Y = 3 : 5