In a survey I have to ask for the number and age of the children of the respondents.

I imagine that the first step would be to ask for the number, and in the next step a table would appear with as many rows as the number they entered, where they have to enter an age in each row. Is this possible?

Yes, you can place relevance on the sub-questions (rows) of Q2 to conditionally display them depending on the anwer to Q1.

See my answer to this post - www.limesurvey.org/forum/can-i-do-this-w...ltiple-choice#155214