Solutions to questions
Candle problem: Empty the box of thumbtacks, put the candle into the box, use the thumbtacks to nail the box (with the candle in it) to the wall, and light the candle with a match.
See illustration below.
Radiation problem: This can be solved by using the analogy of an army general who wishes to capture an enemy fortress, the roads into which are mined in such a way that the passing of any large force will cause an explosion but small groups of men could pass over them safely.
The strategy is to divide the force, attack from different sides and converge on the target.
Nine dot problem: The solution to this literally goes “outside the box”.