Statements: All aeroplanes are trains. Some trains are chairs. Conclusions:  Some aeroplanes are chairs. Some chairs are aeroplanes. Some chairs are trains. Some trains are aeroplanes.

Since the middle term 'trains' is not distributed even once in the/premises, no definite conclusion follows. However, III is the converse of the second premise while IV is the converse of the first premise. So, both of them hold.