Andre Geim explains in his autobiography as follow.
"We solved many problems from old exam papers either from Phystech or, even harder, from international Olympiads. But even more helpful was the way he taught me to deal with physics problems: it is much easier to solve a problem if you first guess possible answers. Most problems at Phystech level require understanding of more than one area of physics and usually involve several logical steps. For example, in the case of a five-step solution, the possibilities for dealing with the problem quickly diverge and it may take many attempts before you get to the final answer. If, however, you try to solve the same problem from both ends, guessing two or three plausible answers, the space of possibilities and logical steps is much reduced. This is the way I learned to think then and I am still using it in my research every day, trying to build all the logical steps between what I have and what I think may be the end result of a particular project. After a couple of months, my tutor no longer asked me to write up a solution. Instead, I just explained verbally the way I would solve a particular problem – all the logical steps required to get to its end without describing routine details. This allowed us to go through the problems at lightning speed."
