smc

Without loss of generality, let the price of the article be 100. Thus, the new price is $.9\cdot 100=90$. Then, to restore it to the original price, we solve $90x=100$. We find $x=1\frac{1}{9}$, thus, the percent increase is $1\frac{1}{9}-1=\frac{1}{9}=\boxed{11\frac{1}{9}\%}$.