### Riddle

Each of the 100 people there must shake 99 hands. But if I shake your hand, this is one handshake, not two, so divide 9,900 by two. **The answer is 4,950.**

One might have thought that someone trained in mathematics or science would answer this easily by applying rigorous logic, while a student of the humanities might flounder. (Incidentally, C. P. Snow's Rede Lecture which started the Two Cultures controversy was given in Cambridge just half a century ago.) But it's not quite as simple as that.

A teacher of mathematics of my acquaintance (no names, she knows who she is) talked about factorials for a bit, then decided that it involved triangular numbers and gave up. Another acquaintance, equally intelligent, who had studied Latin and Greek, went off at a tangent and got it wrong.

My guess is that anyone with a bit of gumption can solve it easily unless he or she is side-tracked by a bit of irrelevant knowledge or excessive cleverness.

Now you can tell the person of integrity either to burn the envelope or to open it and admire your gumption.