The Modelski Chain Rule:
(1) Look intently at the problem for several minutes. Scratch your
head at 20-30 second intervals. Try solving the problem on your
(2) Failing this, look around at the class. Select a particularly
(3) Procure a large chain.
(4) Walk over to the selected student and threaten to beat him severely
with the chain unless he gives you the answer to the problem.
Generally, he will. It may also be a good idea to give him a sound
thrashing anyway, just to show you mean business.