Off course 1) the notion of 'far' would have to be defined. As well as 2) what counts as a 'random problem'. And of course 3) different people can think of different generalizations and can do the problems at different rates.
Let's say 1) An undergraduate degree in mathematics, just to have some milestone. 2) Let's say you take the standard undergraduate mathematics books used in universities and you pile all the problems on a big heap, you randomly take a problem one after the other. If you come across a problem that is included in some generalization of another one, you skip it. 3) Let's say we're talking about an average undergraduate in mathematics who is beginning his studies.