The meaning of the decimal representation of a number $0 . d_{1} d_{2} d_{3} \ldots$. (where the digit $d_{i}$ is one of the numbers 0,1 , $2, \ldots, 9$ ) is that
$$0 . d_{1} d_{2} d_{3} d_{4} \ldots=\frac{d_{1}}{10}+\frac{d_{2}}{10^{2}}+\frac{d_{3}}{10^{3}}+\frac{d_{4}}{10^{4}}+\cdots$$
Show that this series converges for all choices of $d_{1}, d_{2}, \ldots .$