If the base of a rectangle is increased by $10\%$ and the area is unchanged, then the altitude is decreased by:
$\textbf{(A) \ }9\%  \qquad \textbf{(B) \ }10\% \qquad \textbf{(C) \ }11\% \qquad \textbf{(D) \ }11\frac{1}{9}\% \qquad \textbf{(E) \ }9\frac{1}{11}\%$
$b\cdot a=\frac{11}{10}b\cdot xa\implies x=\frac{10}{11}$. Hence, the altitude is decreased by $1-x=\frac{1}{11}=\boxed{\textbf{(E)}\ 9\frac{1}{11}\%}$.