The oxidation number of ‘$Mn$’ in potassium permanganate is
 

It is given to find out the oxidation state of $Mn$ in potassium permanganate .

Potassium permanganate ${\mathrm{KMnO}}_4$

Oxidation state of $K$ is $+1$

Oxidation state of $O$is $-2$

Let oxidation state of $Mn$ be $x$

Oxidation state of $Mn$ in ${\mathrm{KMnO}}_4$ : 

$$\begin{gathered} +1 + x + 4 (-2) = 0 \\ +1 + x - 8 = 0 \\ x - 7 = 0 \\ x = +7 \end{gathered}$$