According to the balanced reaction; 

1 mole of ${\mathrm{MnO}}_4^{-}$​ consume 5 moles of Fe²⁺

So, 5 times of FeSO₄​ will be equivalent to 50 ml since the molarity is same in ${\mathrm{MnO}}_4^{-}$​ and Fe²⁺.