To Ag₂CrO₄ solution over its own precipitate, ${\mathrm{CrO}}_4^{2-}$ions are added. This results in

$$\begin{gathered} {\mathrm{Ag}}_2{\mathrm{CrO}}_4\rightleftharpoons 2{\mathrm{Ag}}^{+}+{\mathrm{CrO}}_4^{2-} \\ {\mathrm{K}}_{\mathrm{sp}}={\left[{\mathrm{Ag}}^{+}\right]}^2+\left[{\mathrm{CrO}}_4^{2-}\right] \end{gathered}$$

As K_sp remains constant, addition of ${\mathrm{CrO}}_4^{2-}$ will increase its concentration, resulting in decrease in Ag⁺ ion concentration.