I have the following frequency distribution for number of women divorcing
$$ \begin{array}{c|lcr} Age & \text{Divorced} \\ \hline 15-29 & 11 \\ 30-39 & 26 \\ 40-44 & 21 \\ 45-49 & 18 \\ 50-54 & 11 \\ 55-64 & 13 \end{array} $$
My question is: How do I find the interval which contains the median, considering the fact that the intervals are not uniformly distributed?
You have a total of $100$ observations, so the median is just the average of the $50$th and the $51$st observation (when observations are ranked in ascending order, as they are here).
In which interval do you find these observations? Are the lengths of the intervals of any importance for this question?
The lengths of the intervals - actually only the length of the interval that contains these observations - may be of an importance when you want to calculate the exact value of the median (and not it's location, in terms of intervals, as you do here).