People are allowed to add an apple or take an apple from…

People are allowed to add an apple or take an apple from a large barrel. If people are only adding apples, the barrel can be filled in 5 hours. If people only take apples, the barrel can be emptied in 15 hours. If it is desired that the barrel should be filled, from empty, exactly 6 hours after people begin adding apples at 9:30am, then at what time should people begin taking apples?

AQuA-RAT — Algebra Question Answering with Rationales (Ling et al., DeepMind, 2017) · train #27026