## Think and solve!
Since 1974, when the traditional
The problems are always published with a solution, hidden somewhere
in the same issue of the journal. However, we will not provide
solutions here. Try for yourself. And if you really cannot find
anything and you are sure you do not want to continue trying,
but you still wish to know the solution, write to pawelst@mimuw.edu.pl or
bartol@mimuw.edu.pl and
ask for one. In order to make our communication easier, we preserve
the original numbers of the problems as they appeared in
In this issue we offer you three mathematical problems by
M 823. Non-zero vectors M 824. Assume that some three orthogonal sections of a convex polyhedron which has a center of symmetry are squares. Does that necessarily imply that the polyhedron is a cube?
M 825. Prove that if |