Earlier quoted context omitted.
I have done that occasionally. They complain, but only in jest.
You've handed out a math assignment that was an open unsolved problem and not told your students what you had done prior to them leaving for the day?
Yes.
and not told your students what you had done prior to them leaving for the day?
No. As the comment I responded to says: I
reveal the full truth after they have been working for fifteen minutes or so.