This is a puzzle that I have seen in many different sources, a nice geometry puzzle!
Mary baked a rectangular cake. Merlin secretly carved out a small rectangular piece, ate it and vanished! The remaining cake has to be split evenly between Mary’s two kids. How could this be done with only one cut through the cake?
I would strongly encourage parents to actually draw this out for the children with the rectangles of different sizes and placed at awkward angles.
As always, please send your answers to firstname.lastname@example.org